remove public/js/libs dir

Getting ready for browserify which won't be needing these files.
use Browserify

Use browserify to manage modules and dependencies. Needed to shim Ember
and Ember Data as they are the two non browserify compatible libraries.

In dev, use `npm run watch` to watch for changes and browserify will
rebuild the app.js file.
remove Gruntfile

no longer using grunt to build. will probably use gulp in the future
missing semicolon
use min ember-data for browserify

Unminified ember-data calls `require`, mistaking it for browserify's
require which causes a cannot find module error. We could use derequire
but that would require a more complicated build step that I may
implement in the future. For now, just use the minified ember-data
which doesn't use `require`.