Merge pull request #31 from kbaird/master

Adds the #download and #play methods to Helix::Document
Merge pull request #33 from rebekah/master

Updating the Library find method so that it can take optional content_ty...
Merge pull request #34 from rebekah/master

small refactoring of the Library#process_opts method
Move process_opts up to the class level in lib/helix/library.rb

Bump version to 0.0.5.0.pre
Raw uncommented changes for Playlist.guid_name being id instead of playlist_id
Adding a comment to Kevin's Playlist guid_name method