Protocol agnostic javascript src

The small change allows the product to work on Plone sites when viewed over SSL.

A URL like this:
http://www.google.com/coop/cse/brand?form=cse-search-box&lang=en

Changed to this:
//www.google.com/coop/cse/brand?form=cse-search-box&lang=en

Means that the js will be grabbed via whatever protocol was used to deliver the page.

I appreciate all your hard work. We just started using collective.gcs on cnm.edu and it's been a huge value to us!
Thanks.