Fix the method for belongsTo with correct receiver

lib/include.js

@@ -119,9 +119,8 @@ Inclusion.include = function (objects, include, cb) {
         }
       }
       var inst = (obj instanceof self) ? obj : new self(obj);
-      var relationMethod = inst[relationName];
-      // FIXME: [rfeng] How do we pass in the refresh flag?
-      relationMethod(function (err, result) {
+      // Calling the relation method on the instance
+      inst[relationName](function (err, result) {
         if (err) {
           return callback(err);
         } else {

lib/relations.js

@@ -340,10 +340,13 @@ Relation.belongsTo = function (anotherClass, params) {
 
   // Define a property for the scope so that we have 'this' for the scoped methods
   Object.defineProperty(this.prototype, methodName, {
-    enumerable: false,
+    enumerable: true,
     configurable: true,
     get: function () {
-      var fn = relationMethod.bind(this);
+      var fn = function() {
+        // Call the relation method on the declaring model instance
+        return relationMethod.apply(this, arguments);
+      }
       // Set the remoting metadata so that it can be accessed as /api/<model>/<id>/<belongsToRelationName>
       // For example, /api/orders/1/customer
       fn.shared = true;