Refreshes documentation

[ashfurrow]

Hello! This PR updates the documentation in this repo to reflect more contemporary practices. The PR does the following:

• Updates the readme docs.
  • Recommends Yarn.
  • Moves to React Native Typescript Transformer instead of using an output directory.
  • Replaces the Enzyme rendering test (which has compatibility issues with React Native) with a snapshot test.
  • Updates the example Hello component to be a bit more modern.
  • Fixes formatting/markdown inconsistencies.
  • Adds a list of helpful resources at the end.
• Deletes all existing code and re-generates it based on the new readme (and in the ExampleProject directory).

Thanks to @orta for his help working through this.

Fixes #34.

[msftclas]

All CLA requirements met.

[orta]

We've moved these changes to also be on the React Native blog ^

[phwb]

Hi, you are going to merge this PR? I want to translate this guide in to russian languge, but i want to do this with newest inforamtion.

[ashfurrow]

You got it, I'll get those changes in today. Thanks!

[orta]

These changes will need to be migrated over to the RN blog post too 👍

[ashfurrow]

Good idea @orta, I've done that here: https://github.com/facebook/react-native-website/pull/282/commits/fad2e8556d6322da9873138cbd92cb74e08c907e

[orta]

Poke

[bryantee]

Are we just waiting for @DanielRosenwasser to approve changes?

[DanielRosenwasser]

Thank you so much for all the work here!! 😄 ⭐️ 👏

[ashfurrow]

🎉🙇🤗