fix(server): MONGOLAB_URI -> MONGODB_URI

fixes #1838

[skip ci]

Author: Awk34

Diff for: templates/app/server/config/environment/production.js

@@ -15,7 +15,7 @@ module.exports = {
 
   // MongoDB connection options
   mongo: {
-    uri:  process.env.MONGOLAB_URI ||
+    uri:  process.env.MONGODB_URI ||
           process.env.MONGOHQ_URL ||
           process.env.OPENSHIFT_MONGODB_DB_URL +
           process.env.OPENSHIFT_APP_NAME ||