RequireJS Plugin

Just a quick plugin to execute r.js optimizer from command line, bundle javascript files and compress them through r.js. Extends `CLTransformer` (in quite a similar way as the LESS plugin does). Includes integration tests. Tested with r.js version 2.1.4 upon node v0.8 on a linux box.

This is more like a first drop towards a more sophisticated plugin accepting options through site settings. Right now it just does the job by reading `rjs.conf` options file and simply bundling all JS modules together to a destination file called `app.js`.