feat(testing): Add a debug mode for testing

If you want to use the `debugger` statement to pause execution
during your tests, you need to have karma started in a particular way.
This lets you do `grunt test:debug`, which will cause the tests to be
run in Chrome, and will keep the browser open.

After Chrome is launched, you must manually open Chrome's web inspector
before the `debugger` breakpoints will be respected
Merge pull request #611 from rackerlabs/debug_mode

feat(testing): Add a debug mode for testing