Run static analysis on Travis CI

[hugovk]

Basic CI tests using https://github.com/hugovk/python-ci-static-analysis: pyflakes looks for possible bugs, pep8 looks for possible style errors.

For example: https://travis-ci.org/hugovk/google/builds/202960528

Groundwork for https://github.com/MarioVilas/google/issues/21.

@MarioVilas Please will you:

• [ ] Create a free Travis CI account
• [ ] Enable your repo at https://travis-ci.org/profile (you may need to Sync account first)
• [ ] Push a commit to your repo, and Travis CI will run the static analysis

[hugovk]

Rebased on master and updated.

Example: https://travis-ci.org/hugovk/googlesearch/builds/327237005

[MarioVilas]

Awesome work, thanks! :)