jwage/purl — pull request #14 by MPV (2013-06-19 08:47:29+00:00)
Title: Adding support for "protocol relative" / "schemeless" URLs

...or "network-path reference" as it's called by the RFC:
http://tools.ietf.org/html/rfc3986#section-4.2

Here's the related issue: https://github.com/jwage/purl/issues/13