[Android] naturalSize callback to match iOS version.

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

fix screenPhysicalPixels error