React: Modernize release process

It's way too much work to do a React release right now. It's mostly muscle memory for me at this point but it should be easy for anybody to do it. Historically I kept certain steps manual because I screwed things up and wanted to be able to pause and double check.

There are a few things contributing to the difficulty:

• use of react-bower repo as the first push target
  
  
  
  • which is a result of fb.me link generation / CDNization needing to happen on internal FB infra
  
  
• manual steps across multiple repos
• manual version modification
• assets needing to be in multiple places, copied across branches

A few ideas:

• we should be able to differentiate between pre- and final releases. It should be a single command to ship a new alpha at any point and they should be lightweight.
• final releases need a little more since they will get installed by default by people and have additional requirements (eg changelogs, assets in multiple places)
• npm run release which then does all the things. It could be an interactive process
• start using the GitHub releases APIs to store build assets, cutting out steps
• set up cdn.reactjs.org and just host our builds there, dropping fb.me entirely (risk, we have to run this forever…)
  
  
  
  • alternatives: work with existing CDNs and make sure we can have versions deployed on command (pull based autoupdating can result in delays, things like jsfiddle, our tutorial need assets available immediately)
  
  
• investigate lerna, could be helpful with the multiple packages we have, though we ideally want to disentangle the releases