Fix react-tools module

I messed this up pretty badly and didn't include react *at all*.

Test Plan: npm pack && npm install <packed.tgz>, then require('react-tools')`

main.js

@@ -1,6 +1,6 @@
 'use strict';
 
-var React = require('./build/React');
+var React = require('./build/react');
 var visitors = require('./vendor/fbtransform/visitors').transformVisitors;
 var transform = require('./vendor/fbtransform/lib/transform').transform;
 

package.json

@@ -16,7 +16,7 @@
     "README.md",
     "main.js",
     "bin/jsx",
-    "build/React.js",
+    "build/react.js",
     "vendor/fbtransform/",
     "vendor/woodchipper.js"
   ],