Update Browser address bar when navigating between playlists
Rename CSS file for navigation
Remove position relative on container

[bugfix] when clicking quickly on nav arrows, it would select the whole
page and add this ugly blue highlight layer
Split the javascript initialzing code in two script tags

that allows the backbone code in local (aka even when the SC object is
undefined)
Add has_prev_playlist and has_next_playlist flags to Playlist#as_json
Add some TODOs
Display navigation buttonsonly when relevant
Reorder methods in PlaylistsView
TODO - Deal with prev/next buttons behaviors
Refactor _javascript.haml
Add track.json to lib files
Add Heroku gem for asset compilation on prod