Fix playerviewcontroller keypath leak of observers

The progress message handler will duplicate recursions of the `onProgressMessage` handler on change of player state from any state to STATE_READY with `playWhenReady` is true (when video is not paused). This clears the messages on STATE_IDLE and STATE_BUFFERING to break the recursion.

fix typo in README

- Bump Exoplayer to 2.10.4
- Remove deprecated usages of Exoplayer methdos
- Add `ReactExoplayerConfig` as extension points to configure the Exoplayer instance

Fixed Exoplayer doesn't work with mute=true #1696

Added support for automaticallyWaitsToMinimizeStalling property on iOS 

Removing the call to observeValueForKeyPath:ofObject:change:context: …

Updated README.md to include instructions for React Native 0.60 and a…

[FIX] Fix release 5.0.0 bad merge with 5.0.1

fix crash iOS9

If the super class is not actually observing the key, the app will crash. Checking to see if
the super class responds to this selector doesn't solve this issue.

react-native-video github issue: https://github.com/react-native-community/react-native-video/issues/1515

Discussion about this particular problem: https://stackoverflow.com/questions/6574714/whats-wrong-with-this-observevalueforkeypathofobjectchangecontext-implement

(cherry picked from commit 2f23cc021c2e61410076c2f05da334907479280f)

(cherry picked from commit b0737bd56a4743c5154f48533a2f097ec59622a5)