FIX: Don't rewrite urls to be absolute, if they are a URI with a protocol.
This is determined in this fix by the existence of a colon ':', to show the uri has a protocol.
FIX: Updated protocol check to become more stringent.
Merge pull request #1957 from jedateach/uri-rewriting-patch

FIX: Don't rewrite urls to be absolute, if they are a URI with a protocol