Call updatePlaybackStats() from within seekTo().

This addresses an issue that @christurvey brought up in https://github.com/GoogleWebComponents/google-youtube/pull/19 in a slightly different manner.

It explicitly calls `updatePlaybackStats()` following a `player.seekTo()` after waiting for a small bit of time to give the YouTube player time to update its internal state.

(It would be lovely if there were some event-driven way to detect that the YouTube player's state had updated, but unfortunately that's not the case.)