Compress CSS files into one source

Using require.js optimizer to compress all CSS into a single file.

Set up `grunt` to allow developers to run both a server and a 'debug' mode where the original non-compressed files are pulled in.

Change `/js/app/main.js` to `/js/app.min.js` to play with minified JavaScript file. At present I haven't implemented this as there is a problem with integrating `backbone-indexeddb` and optimisation. I am told that Backbone is not defined, eventually it pops up  on the window object (where backbone-indexeddb would pick it up, but too late it seems).

My backbone knowledge is non-existent and my requirejs knowledge isn't that great. I'd imagine @rodrigods could sort this, or maybe we could get @julien51 to take a look?