RubaXa/Sortable — pull request #55 by PeterDaveHello (2014-07-10 07:41:06+00:00)
Title: use protocol-relative URL to load libraries

browser will tell users that the page contains some insecure resources, use protocol-relative URL can prevent this issue.

reference : [The Protocol-relative URL](http://www.paulirish.com/2010/the-protocol-relative-url/)