Let's slim the text down as much as possible here. How about:

> We've updated the X-Ray Goggles, and we think you're going to love it!
> You can now save your remixes to your own personalized domain.
> To install the new bookmarklet, head over to https://goggles.webmaker.org.

Removing the webmaker.org link also limits the message to one call-to-action, so nobody who's interested in updating the bookmarklet ends up lost on Webmaker.org.