Add methods to delete a song/party.

Signed-off-by: Aron Cedercrantz <aron@cedercrantz.se>
Add a method to refresh a model object from parse.

Signed-off-by: Aron Cedercrantz <aron@cedercrantz.se>
Fix a possible null-pointer exception.

Signed-off-by: Aron Cedercrantz <aron@cedercrantz.se>
Add method to get or create song by Spotify URI.

Signed-off-by: Aron Cedercrantz <aron@cedercrantz.se>
Add method to get a specific party.

Signed-off-by: Aron Cedercrantz <aron@cedercrantz.se>