Add exports to globals for jshint

This is a bit unfortunate, but it'll shut lint up for the time being. We
can't just change the modules to use `module.exports = { ... }` due to
how we handle circular dependencies internally (`ReactMount` require
`ReactID` and vice versa).

Author: zpao

src/.jshintrc

@@ -21,6 +21,7 @@
   "globals": {
     "__DEV__": false,
     "require": false,
-    "module": false
+    "module": false,
+    "exports": false
   }
 }