add in coveralls CI code coverage tracking

[danmayer]

While our tests output code coverage it is a bit had to visualize and compare coverage over time... Let's add in https://coveralls.io/ support to our CI test runs to make it easy to see that we are maintaining and increasing our coverage.

added as help wanted / good first issue to see if we can get some more contributors ;)

[dondonz]

Hello! If this hasn't already been taken, I would like to help.

[danmayer]

That would be awesome @dondonz let us know if you need anything to get started

[dondonz]

Thanks!

I've given it a go (PR #157), please let me know what you think.

I have two questions.

1. Could someone please log into Coveralls and add the Coverband repo? Perhaps you've already done this 😄
2. Could I confirm - would you like to retain SimpleCov in the test_helper.rb file? I have not changed any SimpleCov settings.

[danmayer]

hmm good call not sure if I still need SimpleCov I will take a look.