RSB -- github has removed git protocol support

[Joel Sherrill]

Hi

github has disabled the git protocol and wants people to use the https or
ssh protocol. There are a handful of github git:// URLs in the RSB master
and possibly more in the 5 branch. I have no idea right now what the rule
is to convert the URLs from git to https ones.

This is a warning to the community and a plea for help in converting the
URLs.

Thanks.

--joel