Add proposal form

Closes #6

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

app/controllers/proposals/new.js

@@ -0,0 +1,27 @@
+import Ember from 'ember';
+import QueryParams from 'ember-parachute';
+
+export const queryParams = new QueryParams({
+  recipient: {
+    defaultValue: ''
+  },
+  amount: {
+    defaultValue: ''
+  },
+  url: {
+    defaultValue: ''
+  },
+  ipfsHash: {
+    defaultValue: ''
+  }
+});
+
+export default Ember.Controller.extend(queryParams.Mixin, {
+
+  actions: {
+    onSave() {
+      this.transitionToRoute('index');
+    }
+  }
+
+});