Fix typo
Remove spurious setting of TimedItem._timeDrift
Purge the cached document time when setting up timing
Add tests to check that TimedItem is updated when calling Timeline.play()
Make updates to Player.currentTime take immediate effect
Make updates to Player.startTime take immediate effect
Make updates to Player.source take immediate effect
Merge pull request #169 from steveblock/updateOnPlay

When setting properties on Player, immediately update its TimedItem