Replace deprecated react-tools with babel

- Switch to babel, since react-tools has been deprecated since June 12,
2015. See
https://facebook.github.io/react/blog/2015/06/12/deprecating-jstransform
-and-react-tools.html

- Move babel command to "npm run build"

- Move commands for package into "bin/package.js"

.babelrc

@@ -0,0 +1,5 @@
+{
+  "presets": [
+    "react"
+  ]
+}