Write tests

[arthurvr]

I'd like to explore how to test this extension. It's probably not as easy as the yeoman built-in mocha suite, as this is a devtools extension.

If it really brings up interesting changes to the build system we might as well contribute those back to the generator.

Low priority though.

[pbakaus]

Just finished my investigation (good a really quick reply internally!). Apparently some solid instructions here: http://stackoverflow.com/questions/2869827/how-to-test-chrome-extensions