Using a protocol-independent absolute path for google fonts

Using a protocol-independent url is better, especially when the website use https to transfer the webpage, just let the browser to decide which protocol it will prefer to use.
reference : http://www.paulirish.com/2010/the-protocol-relative-url/
Merge pull request #21 from PeterDaveHello/patch-1

Using a protocol-independent absolute path for google fonts