Added React import to android VideoPlayer Example

Added possibility to play video in background and when app is inactive.

[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

Import for React was missing in index.android.js of VideoPlayer, without which the example would not run.

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