No, Davey, that protocol-independent URL is correct. It will choose the protocol (HTTP or HTTPS) depending on the protocol with which the page is currently served, to prevent unsafe content to be loaded in a secure environment.
That code looks correct and should actually work. What is the error console saying? Can you give us a link? Try to add the missing
attribute to the script element.
Also, instead of “document ready” you can and should use the shortcut:
// your code here