add instructions for CocoaPods setup

Note: you can also use the `ignoreSilentSwitch` prop, shown below.

</details>

<details>

  <summary>iOS (CocoaPods)</summary>

Setup your Podfile like it is described in the [react-native documentation](https://facebook.github.io/react-native/docs/integration-with-existing-apps#configuring-cocoapods-dependencies). 

Depending on your requirements you have to choose between the two possible subpodspecs:

video only:

```diff

  pod 'Folly', :podspec => '../node_modules/react-native/third-party-podspecs/Folly.podspec'

+  `pod 'react-native-video', :path => '../node_modules/react-native-video/react-native-video.podspec'`

end

```

video with caching (you can learn more about caching [here](docs/caching.md):

```diff

  pod 'Folly', :podspec => '../node_modules/react-native/third-party-podspecs/Folly.podspec'

+  `pod 'react-native-video/VideoCaching', :path => '../node_modules/react-native-video/react-native-video.podspec'`

end

```

</details>

<details>

  <summary>tvOS</summary>

# Caching

Caching is currently only supported on `iOS` platforms with a CocoaPods setup.

# Technology

The cache is backed by [SPTPersistentCache](https://github.com/spotify/SPTPersistentCache) and [DVAssetLoaderDelegate](https://github.com/vdugnist/DVAssetLoaderDelegate).

# How Does It Work

The caching is based on the url of the asset.

SPTPersistentCache is a LRU ([last recently used](https://en.wikipedia.org/wiki/Cache_replacement_policies#Least_recently_used_(LRU))) cache.

By default files expire after 30 days and the maxmimum cache size is 100mb.

In a future release the cache might have more configurable options.