DOC: Deprecate README, add README.md
    
    To make it easier to display the contents of README on the project
    homepage, this patch converts the README contents to README.md.
    
    The original README is removed so that we don't maintain two different
    sources.
    
    The links to fedorahosted are retained until we migrate the wiki pages.
    
    Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>
    Reviewed-by: Fabiano Fidêncio <fidencio@redhat.com>