Move to using `jstransform` and `esprima-fb` npm modules

I've published `jstransform` and `esprima-fb` as npm modules now, so this moves react to use those npm modules.
To do this, I've deleted all the src transformation stuff from `vendor/fbtransform` (except the react-specific transform visitors) and I've moved the package.json deps away from pointing at the facebook esprima github branch and over to the versioned npm module.

I ran `npm test` to verify that I didn't break anything, but that's all I did -- so if there's anything else I should be doing to make sure I didn't break stuff please let me know.