Refectoring continued

[trichter]

This PR supersedes PR #4.

The following work was done in this branch:

• tests moved inside module to provide them on pypy
• tests can now be run from any directory, because model files are dynamically discovered
• the notebook codes are run with the tests, which guarantees that these codes don't break in the future
• the conf module was removed, instead the relevant arguments can be directly passed to run_plane e.t.c
• therefore it is not necessary anymore to check if global variables are correctly set
• A Model object was added to store the model related variables, it is easy now to change just a few parameters and call run_plane again.
• calc_ttime example was simplified and the output corrected to s
• add badges with links to travis-ci and coverall to the readme
• add new pytest call to readme and add additional install instructions
• updated the notebooks to the new api

@paudetseis When the tests pass and you are happy with the changes this can be merged.

[codecov-io]

Codecov Report

:exclamation: No coverage uploaded for pull request base (master@8aafd8d). Click here to learn what that means. The diff coverage is 83.39%.

@@            Coverage Diff            @@
##             master       #5   +/-   ##
=========================================
  Coverage          ?   55.82%           
=========================================
  Files             ?       10           
  Lines             ?     1141           
  Branches          ?        0           
=========================================
  Hits              ?      637           
  Misses            ?      504           
  Partials          ?        0

Impacted Files	Coverage Δ
telewavesim/tests/test_0_imports.py	100% <ø> (ø)
telewavesim/conf.py	0% <ø> (ø)
telewavesim/doc.py	0% <0%> (ø)
telewavesim/tests/test_routines.py	100% <100%> (ø)
telewavesim/tests/test_notebooks.py	100% <100%> (ø)
telewavesim/tests/test_utils.py	100% <100%> (ø)
telewavesim/wiggle.py	47.56% <7.69%> (ø)
telewavesim/utils.py	71.09% <79.16%> (ø)

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