Improve anonymous fedpkg usage instructions
    
    Old instructions failed at 'fedpkg commit' line.
    Replaced with working sequence of 'git' commands.
    There does not seem to be a way to use fedpkg with freely named
    branches,
    and even if there was,
    using fedpkg as a git wrapper does not really make anything easier.
    
    Also remove reference to wiki page about HTTPS-Commits.
    The page seems to be seriously outdates
    and does not contain useful information for anonymous fedpkg users.
    
    Resolves #64