Better timeout handling

Right now, each time we create a timeout or interval within an instance of the player, we must also set up `dispose` listeners to clean up those timers. This PR adds a `setTimeout` and `setInterval` method on the player that behaves exactly the same as those native functions except they automatically add the dispose listener.
we probably should just capture `player()` as a variable, it's silly to call this function 4 times in two lines.