Do not build with Ruby 1.9.3 on Travis
Create Albums#new, #create, #edit and #update
Create Album#artist_name convenience method
Create Albums#new and #edit views
Add link to artist from album show view
Add link to artist from song show view
Authorize Songs#edit and #update
Add authorization rules for AlbumsController
Authorize AlbumsController actions
Add link to create new song from album show view