chore(server): Move api-server in to it's own DIR

api-server/common/models/challenge.js

@@ -0,0 +1,12 @@
+import { Observable } from 'rx';
+
+export default function(Challenge) {
+  Challenge.on('dataSourceAttached', () => {
+    Challenge.findOne$ =
+      Observable.fromNodeCallback(Challenge.findOne, Challenge);
+    Challenge.findById$ =
+      Observable.fromNodeCallback(Challenge.findById, Challenge);
+    Challenge.find$ =
+      Observable.fromNodeCallback(Challenge.find, Challenge);
+  });
+}