Calculate coverage and submit to coveralls.io

That was there before @stvstnfrd got there. Before my big refactor merged, that was the Travis test line in use. I got the tests fixed up so you could just run nosetests and run everything, but I decided to leave the old line there as an example of how you use nosetests to test just part of the stuff. I think it's a nit, but agree it can be removed.