Fix font link to pass validation

Dropped http in favor of protocol-relative link so browsers won't throw errors about including insecure content if using https.

Replaced the illegal pipe character with url encoded value %7c to pass validation.
Error from validator.w3.org: "Bad value http://fonts.googleapis.com/css?family=PT+Serif:400,400italic,700|PT+Sans:400 for attribute href on element link: Illegal character in query: not a URL code point."

Removed PT Sans size specification as 400 is the default so it's redundant.