Load contributions from cache if present

And then fetch more from network. Also, only load 30 from network before
first render (with nothing cached), then load more after the page has
rendered.

app/routes/application.js

@@ -27,6 +27,7 @@ export default Route.extend({
         if (this.kredits.contributorsNeedFetch) {
           schedule('afterRender', this.kredits, this.kredits.fetchContributors);
         }
+        schedule('afterRender', this.kredits, this.kredits.fetchContributions);
       });
   }
 });