Added temporary playground page for testing the new Player API
Added cancel() to Player
Added player seeking shortcut
Made logging togglable and added additional log targets
Updated playing attribute to match spec more closely (has weird dependency on paused state)
Added player.finish() shortcut
Added _pauseTimeLag logging
Merge pull request #500 from alancutter/newPlayerAPI

New Player API: Add extra step to seek method
Only bound players when they reach the end of their content with respect to their playback rate direction
Added button to player API playground to seek to -1s.