added support for rnpm

package.json

@@ -18,6 +18,11 @@
     "react",
     "android"
   ],
+  "rnpm": {
+   "android": {
+     "packageInstance": "new ExtraDimensionsPackage(this)"
+   }
+  },
   "author": "Jack Hsu <jack.hsu@gmail.com> (http://jaysoo.ca/)",
   "license": "ISC"
 }