Stop annoying the user with update messages

[mattrayner]

We'd like to let the user know if there's a new version of the bookmarklet - especially if there is a security concern or a major update that we think they should have.

How can we do this?

We can use cross-domain data storage as a method of persistently finding whether a user has been prompted already.

Possibly based on this post with XAuth:
http://www.nczonline.net/blog/2010/09/07/learning-from-xauth-cross-domain-localstorage/

[mattrayner]

I'm thinking that an update page isn't necessary - I'll probably just put some progress-style div at the top of the page with a link to an update page