Make it browserify-friendly

Because `main.js` uses ES2015, this tells browserify to compile it with babelify first.

package.json

@@ -7,6 +7,11 @@
     "url": "https://github.com/christianalfoni/formsy-react.git"
   },
   "main": "src/main.js",
+  "browserify": {
+    "transform": [
+      "babelify"
+    ]
+  },
   "scripts": {
     "start": "webpack-dev-server --content-base build",
     "deploy": "NODE_ENV=production webpack -p --config webpack.production.config.js",