Getting codecov up and running in TravisCI

[endy-imam]

One of my key worries when trying to create unit tests for the project is wondering if I tested all of the appropriate functions in a given module.

This issue is brought up when trying to create a controller test for issue #20 and my concern is struggling to figure out how to even test functions such as on_session_started and on_session_ended that as of now doesn't seem to have a purpose.

Another is the stray codecov command in the after_success section of the .travis.yml that while it was called, it was never properly executed as shown under:

$ codecov
codecov: command not found

I am gonna get around trying to get this working so we can be confident that all other functions won't cause unforeseen issues down the line.