Add proposal form

Closes #6

Form can be prefilled using query params on the route. The params are
`recipient`, `amount`, `url` and `ipfsHash`.

app/router.js

@@ -8,6 +8,9 @@ const Router = Ember.Router.extend({
 
 Router.map(function() {
   this.route('spinner');
+  this.route('proposals', function() {
+    this.route('new');
+  });
 });
 
 export default Router;