Run tests for Mocha

[simonihmig]

Currently there is no infrastructure to test the Mocha side of things.

We should figure out how to run the whole test suite for Mocha as well. Using ember-try it would probably be possible to write scenarios that remove ember-qunit and add ember-mocha. We still have the issue that the step files are coupled to qunit (example), so some way to add dual support for both testing frameworks in a single file, or exchanging the step files with some other mocha based ones would be needed...