If a user navigates to a UV link directly, without the service worker
registered, Cyclone's bare server will take over and interpret the URL
as http://go/..., which you definitely didn't want, unless you happen
to work at Google :P
In Cyclone's fetchBare(), the content type wasn't correct, and the
status line should be "Internal Server Error", not just "Error". In
the main request handler, I added similar error handling, just in case.
The error handling in the catch block led to a bug where the request's
body was piped to Cyclone's response. However, since the mock request in
the catch block doesn't have a body property, let alone a pipe method,
that line throws an error.
