Merge pull request #344 from sankethkatta/master

fix(migration): remove check for undefined on down migrations.

Author: wzrdtales

lib/skeleton.js

@@ -121,8 +121,8 @@ var Skeleton = Class.extend({
       if( migration instanceof Promise ) {
 
         migration
-        .then(function( Promise ) {
-          if( Promise !== undefined && cb_executed === false ) {
+        .then(function() {
+          if( cb_executed === false ) {
 
             cb_executed = true;
             resolve();