Add support for complete urls instead of only paths to API call methods
Add support for starred playlists in Playlist.find
Use href in Playlist#tracks and #complete! instead of constructing the url. With this, support for starred playlist comes for free. Added specs for #tracks and #complete! plus some improvements to the playlist spec (use let for variables)
Replace href with @href to bypass method_missing. Use @href in methods Playlist#add_tracks!, change_details! and replace_tracks!
Merge pull request #23 from alexquintino/add_support_for_starred_playlists

Add support for starred playlists