Feature/imperative controls

[niklasdahlheimer]

I've needed the option to programmatically set playback position and control play/pause declaratively.

I also:

• optimized the timing for attaching the eventHandlers (was hardcoded 1000ms before)
• added a event "initialized" to inform when the player is loaded (on my React native apps all other player events (i.e. loadeddata...) where only triggered after manual user interaction, so there where no indicator if the video container is ready and playback position could be set

Things to do:

• Examples needs adjustment.
• eventually add more methods (currently play() pause() mute() unmute() seekTo() are supported

[niklasdahlheimer]

Related to #65 and #58