Colorize output and warn about potential bad karma
    
    This adds colours to karma information to easily distinguish positive,
    negative, and neutral karma. Also, it adds a warning to review the
    reports if neutral or negative karma has been provided. For the user
    Bodhi, the comments are shown in gray color to lessen their visual
    importance.
    
    This commit also adds the --no-color switch that a user can use
    to prevent colorized output on terminals where the colors affect
    readability.
    
    Co-authored-by: Kamil Páral <kparal@redhat.com>
    Fixes: https://pagure.io/fedora-easy-karma/issue/34
    Merges: https://pagure.io/fedora-easy-karma/pull-request/35