GitHub usernames as maintainers

[Clemens Lang]

On Wed, Nov 02, 2016 at 06:45:21PM -0400, Brandon Allbery wrote:
> For me, it looks too much like an email address when combined with
> other things (e.g. "maintainers openmaintainer @foo").

I think that's a formatting problem. We could just as well print
https://github.com/neverpanic in the output of port info --maintainer,
which is (a) not ambiguous, and (b) clickable.

-- 
Clemens