retool api for 0.5.0 (start, state, sync, buffers, timeline)

[bvibber]

Visible API retooling:

• add 'paused' property on AudioFeeder
• guarantee that playbackPosition increases monotonically, except when:
• allow resetting playbackPosition along (with a flush() or not?) in reset() method
• allow compensating for late frames with delay(seconds) method -- injects compensatory silence into the output stream and stops playbackPosition from increasing until the compensation time has passed
  • use this to avoid constant stop()/start() if we're having frame delays; we'll be "actually" back in sync after the next bufferDuration -- that's about 4-5 frames at 24 fps, 5-6 frames at 30fps, 8-10 frames at 60fps
• split out partial interface as TimelineProvider
  • start()
  • stop()
  • reset(newStartTime)
  • delay(seconds)
  • playbackPosition

Flash backend retooling:

• send the playback state from Flash to JS on every call/callback
• flush the output buffer from JS to Flash, if any, on every call/callback (?)

Web Audio backend retooling:

• merge the BufferQueue JS class with the BufferQueue AS class; avoid pre-chunking output by using linked list, and output more cleanly without splitting/merging buffers when not needed

[bvibber]

I don't like the delay() stuff, prototyped it on late-delay branch. Too visibly out of sync.