Merge pull request #47 from mk270/split-docs-gen3

Decouple autogenerated docs material from revision control
give basic stereo player a more sensible stereo panning system.
Mixer doesn't support panning - remove Studio#pan= method
Send control message to @mixer node rather than @mixer_group when setting
main volume
Don't limit volume in studio method, this happens in sound.rb
Merge branch 'master' into split-docs-gen3