Changing preview to use get instead of url

Changing preview to use get instead of url when in production mode. This will ensure waitUntilMobified is called.

Status: **Ready to merge**

Reviewers: @kbingman @marlowpayne 

## Changes
- changed the use of url to get in preview.js

## How to test-drive this PR
- nuke your commands and npm install from this branch
- run your tests, they should work