Fix #707, remove helpers.js and use XMLHttpRequest
Fix #707, remove helpers.js and use XMLHttpRequest

mozilla-services/screenshots,mozilla-services/pageshot,mozilla-services/screenshots,mozilla-services/screenshots,mozilla-services/screenshots,mozilla-services/pageshot,fzzzy/pageshot,fzzzy/pageshot,mozilla-services/pageshot,fzzzy/pageshot,mozilla-services/pageshot,fzzzy/pageshot