Attempt to fix unicode error when using python3.x to make test happy

[sbz]

This PR add the following changes:

Code changes

• Essay to take a stab at fixing the following unicode error raised below when running codemod master branch on python3.x according pyporting guide :

(codemod-3.6) % codemod -m -d . --editor vim --extensions="py" -i '(extensions)' 'sbz test replace \1'
Resume where you left off, at ./build/lib/codemod/helpers.py:47 (y/n)?  y
Searching for first instance...
Traceback (most recent call last):
  File "/private/tmp/test/bin/codemod", line 11, in <module>
    load_entry_point('codemod==1.0.0', 'console_scripts', 'codemod')()
  File "/private/tmp/test/lib/python3.6/site-packages/codemod-1.0.0-py3.6.egg/codemod/base.py", line 493, in main
    run_interactive(**options)
  File "/private/tmp/test/lib/python3.6/site-packages/codemod-1.0.0-py3.6.egg/codemod/base.py", line 79, in run_interactive
    _ask_about_patch(patch, editor, default_no)
  File "/private/tmp/test/lib/python3.6/site-packages/codemod-1.0.0-py3.6.egg/codemod/base.py", line 252, in _ask_about_patch
    terminal.terminal_clear()
  File "/private/tmp/test/lib/python3.6/site-packages/codemod-1.0.0-py3.6.egg/codemod/terminal_helper.py", line 55, in terminal_clear
    if not _terminal_use_capability('clear'):
  File "/private/tmp/test/lib/python3.6/site-packages/codemod-1.0.0-py3.6.egg/codemod/terminal_helper.py", line 75, in _terminal_use_capability
    sys.stdout.write(unicode(capability, 'ascii'))
NameError: name 'unicode' is not defined

• Make happy test suite in python3.x because of doctest print statement issue
• Add python3.x stable version in the travis ci-configuration

Tests verification should be ok after that change

• python2.x:

(codemod-2.7) % make test
py.test --doctest-modules codemod
========================== test session starts  =============
platform darwin -- Python 2.7.14, pytest-3.8.2, py-1.6.0, pluggy-0.7.1
rootdir: /Users/sbrabez/github/codemod, inifile: pytest.ini
collected 18 items

codemod/base.py .                                                                                                                                                                                                                                                        [  5%]
codemod/helpers.py ...                                                                                                                                                                                                                                                   [ 22%]
codemod/patch.py .                                                                                                                                                                                                                                                       [ 27%]
codemod/position.py .                                                                                                                                                                                                                                                    [ 33%]
codemod/query.py ...                                                                                                                                                                                                                                                     [ 50%]
codemod/base.py .                                                                                                                                                                                                                                                        [ 50%]
codemod/helpers.py ...                                                                                                                                                                                                                                                   [ 50%]
codemod/patch.py .                                                                                                                                                                                                                                                       [ 50%]
codemod/position.py .                                                                                                                                                                                                                                                    [ 50%]
codemod/query.py ...

18 passed in 0.12 seconds

• python3.x

(codemod-3.6) % make test
py.test --doctest-modules codemod
========================== test session starts  =============
platform darwin -- Python 3.6.5, pytest-3.8.2, py-1.6.0, pluggy-0.7.1
rootdir: /Users/sbrabez/github/codemod, inifile: pytest.ini
collected 18 items

codemod/base.py .                                                                                                                                                                                                                                                        [  5%]
codemod/helpers.py ...                                                                                                                                                                                                                                                   [ 22%]
codemod/patch.py .                                                                                                                                                                                                                                                       [ 27%]
codemod/position.py .                                                                                                                                                                                                                                                    [ 33%]
codemod/query.py ...                                                                                                                                                                                                                                                     [ 50%]
codemod/base.py .                                                                                                                                                                                                                                                        [ 50%]
codemod/helpers.py ...                                                                                                                                                                                                                                                   [ 50%]
codemod/patch.py .                                                                                                                                                                                                                                                       [ 50%]
codemod/position.py .                                                                                                                                                                                                                                                    [ 50%]
codemod/query.py ...

18 passed in 0.13 seconds

Thank you for this awesome project to help refactoring huge code base!

I hack on this change for Hacktoberfest, please let me know your feedback.

[modocache]

Great, thank you!

[sbz]

@modocache Thank you for merging! It looks like the travis ci integration was disabled for facebook/codemod, so I run a build against my fork sbz/codemod rebased on master. Everything is fine as expected according the build logs \o/