Merge pull request #29 from Peter-Krebs/master

Model: .for() should use object.getPrimaryKey() instead of object.id

Author: robsontenorio

src/Model.js

@@ -69,7 +69,7 @@ export default class Model extends StaticModel {
       throw new Error('The object referenced on for() method is not a valid Model.')
     }
 
-    if (!this.isValidId(object.id)) {
+    if (!this.isValidId(object.getPrimaryKey())) {
       throw new Error('The object referenced on for() method has a invalid id.')
     }
 
@@ -294,4 +294,4 @@ export default class Model extends StaticModel {
     }).then(response => response)
   }
 
-}
+}