improve parsing of fully-protocoled URLs

[Roguelazer]

fixes #193, I think

[Crocmagnon]

Any update on this?

[salemhilal]

@Crocmagnon @Roguelazer yes, actually! We've been triaging issues as of late, but this would be an appreciated contribution.

We've recently fleshed out how JS test framework. Tests would be appreciated before we can merge this, particularly since regular expressions can be tricky to reason about.