Student training dynamic update refactor and tests

* Add tests for dynamic update of student training examples based on rubric changes.
* Use dependency injection for event notification; moved some classes around.
* Move the container JS classes into the Studio minified JS.
* Fix a bug that broke student training updates in Firefox and PhantomJS.
* Move fixture path installation into a common file shared by all tests.

@stephensanchez I moved some things around and renamed a class, so this may be a bit complicated to merge with your changes today.  I'm going to wait until next week to tackle the merge conflicts and test the refactor in a sandbox.