yiiiiikes. Frightening that ANY tests passed with this
add channel_id column to song_plays
associations
when adding a song to a channel, go ahead and record it

Bailing on this conditional and just creating a SongPlay record with
the appropriate associations: user and channel. No need for two
differnet ways to do it. We end up with the same result.
dropping these methods from the api. they're not use or needed.

We add songs to channels, we can handle that there. There's no real
time a user will ever need to have this called on themselves.
Merge pull request #338 from play/channel-plays

Channel Song Plays