Add proposal form

Closes #6

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

app/routes/proposals/new.js

@@ -0,0 +1,15 @@
+import Ember from 'ember';
+import Proposal from 'kredits-web/models/proposal';
+
+export default Ember.Route.extend({
+
+  model(params) {
+    return Proposal.create({
+      recipientAddress: params.recipient,
+      amount: params.amount,
+      url: params.url,
+      ipfsHash: params.ipfsHash
+    });
+  }
+
+});