update JavaScript bindings

Summary:
- adds flow types
- transpiles bundle using babel
- cleans and formats code

Reviewed By: emilsjolander

Differential Revision: D6748362

fbshipit-source-id: fcb5fdde73df6e0062eff1e5038bb5fe0532f997

javascript/.babelrc

@@ -1,5 +1,7 @@
 {
+  "presets": ["stage-3", "es2015"],
   "plugins": [
+    "transform-flow-strip-types",
     [
       "replace-require",
       {
@@ -8,4 +10,4 @@
       }
     ]
   ]
-}
+}