Summary:
React Native Playground has been sunset, so I've replaced the examples that previously used it with examples using [Snack](http://snack.expo.io/).
The examples are directly embedded and can be edited live to see updates. The code itself is also in the docs, so we can easily update the docs in one place and we don't have to actually go to a saved app on Snack and update it there.
Run it locally, go to the `Animations` section and the `Direct Manipulation` section.
Open it on your phone, notice that it falls back to just showing plain code.
<img src="https://cloud.githubusercontent.com/assets/90494/24638547/203ec8fc-189e-11e7-99c8-dfabff949f8d.PNG" width="250">
- Get rid of the Expo new user experience dialog that you see when you open a Snack -- is this a dealbreaker
Closes https://github.com/facebook/react-native/pull/13285
Differential Revision: D4828011
Pulled By: hramos
fbshipit-source-id: 684ad24a14deb72abb8587ffbb726d316f126d75
Brian Vaughn
Fred Liu
Hector Ramos
Brent Vatne
