Treat URLs with a semicolon as invalid
Treat URLs with a semicolon as invalid

Our tests expect URLs with semicolons to be invalid. Our tests are
failing because Ruby's URI library allows semicolons in HTTP urls. I'm
not sure why we were trying to disallow these, but I'd rather disallow
them explicitly just in case there was a good reason.

recursecenter/proxy,recursecenter/proxy,recursecenter/proxy