Authority part parsing fixes

[garyb]

@cryogenian could you review this please?

The change here is that the parsers that optionally accept an Authority would always fail when the authority was not present, as they're supposed to branch depending on whether the authority is present, but instead had an optionMaybe in there.

Fixing the parser this way enables the test cases for ../top_story.htm and top_story.htm to pass successfully now too.

Also a tweak to the pretty printer: usually we'd probably write "foo.htm" rather than "./foo.htm" for a relative file path, but with pathy's normal pretty printing we were getting the latter.

[cryogenian]

👍

[garyb]

Thanks!