Add JSHinting.

Uses the broccoli-jshint package to provide JSHinting support.  broccoli-jshint generates console warning messages as well as QUnit tests so that JSHint errors fail the build.

Screenshot showing things passing on a newly generated application:

![screenshot](http://monosnap.com/image/QXR7tplCZVwJw2dz2XUd8lc7X3AQ7P.png)

Screenshot showing a few errors:

![screenshot](http://monosnap.com/image/c1s0Bo9wR5CubG4pIZRllC3wGxFb8k.png)