Merge pull request #3 from OEP/pmk

fix a few residual references to _cache_raw_timeline
Add RainwaveListener class
Add listeners related to election candidates
Add voting
Remove intermediate rating step
Add RainwaveOneTimePlay class
Add RainwaveChannel.get_listener_by_id()
Pick some nits
Mark songs and albums as favourites
Ignore *.sln files
possible fix for AttributeError on Channel._raw_timeline
hopefully fix deadlock problem; prevent many calls to async/get by adding a stale property (may be implemented naively)