Added option to display the playlist

+ Added option to show the current playlist if the actionBlock of BeamMusicPlayerViewController is not set.
+ Added bar_button@2x.png, playing@2x.png and playlist@2x.png to bundle, to display UI for playlists
# Modified AutoScrollLabel to enable shortcut-scrolling of the playlist table view (scrollsToTop)
+ Added missing connections from xib to BeamMusicPlayerViewController
+ Added BeamPlaylistTableViewCell to display details of a song in a UITableView
+ Added BeamPlaylistViewController to display the playlist in a UITableView
+ Added BeamRadialGradientView to provide a backgroundView for the playlist similar to the music app