Fix Issue 214

It makes no sense if we move observer after calling calling playerWithPlayerItem because this is where the exception raises

Allow to use content:// schema as source.

Happens if someone creates Video component, but doesn't set src to it.

Before: observer removes only in removeFromSuperview, but adds in setSrc – multiple setSrc would add multiple observers and one removeFromSuperview would remove only one observer. Now: Every addObserver in setSrc is balanced by removeObserver also in setSrc

Adding Cookie Support for Android Devices

Fix typo in README

Make visible text *<Video>*  wrapping it with a code block

Additional playback callbacks

fix for RN 0.24+

[iOS] Added orientation to onLoad event.

README: prevent blocking outside music