Setup make lint, added make lint to travis script target.
Added flake8 and pylint as dev requirements.
Added check of ROVI_API_KEY and ROVI_SHARED_SECRET.

 - Only print track-image ( and surrounding markup ) when it's not None.
Return None in 'get_track_image' when r.status_code not ok.
Build and upload wheels
Update README.rst

Fixed typo in first example
Merge pull request #73 from petteraas/optional_rovi_track_image

Added check of ROVI_API_KEY and ROVI_SHARED_SECRET.
Merge branch 'add_lint_target' of https://github.com/petteraas/SoCo
fix pylint complaints