Setup jasmine app for javascript unit testing

This PR adds a new app named "jasmine" that provides a test runner for running javascript unit tests. The javascript unit tests are expected to follow the following conventions:

* Unit tests should be added to the `harvardcards/static/js/spec` directory. The test runner will automatically find and run them.
* Each test file should be named `<mytest>_spec.js`
* Each test should be wrapped in a `define(...)`

You can run the unit tests by loading this URL: `http://localhost:8000/jasmine`. 

@jazahn Can you review this?