FIX for detect relative protocol external links

Some URL's with relative protocol, such as, `//example.com/whatever/` is not detects as external and
ajaxify try to load `http://inteernal.site/example.com/whatever`, which is incorrect.
These regulars expressions fix that and external links detect properly.

Detect code get from http://stackoverflow.com/questions/6238351/fastest-way-to-detect-external-urls and adaptive to ajaxify.

Worked well!