Added LICENSE and 404.js files.

- closed #91 by adding the MIT LICENSE file to root directory.
- added src/pages/404.js from gatsby-starter-default.

src/pages/404.js

@@ -0,0 +1,10 @@
+import React from 'react'
+
+const NotFoundPage = () => (
+  <div>
+    <h1>NOT FOUND</h1>
+    <p>You just hit a route that doesn&#39;t exist... the sadness.</p>
+  </div>
+)
+
+export default NotFoundPage