Limit metadata changes to version number only

This change prevents any whitespace or quotes style changes in
metadata.rb after a version bump.
Add option to configure irc message templates

This adds the option to send different irccat messages specified in the
config. Example:

    plugins:
      irccat:
        template:
          upload: "foo bar! #REDCHEF:#NORMAL %{organization}%{current_user} uploaded #GREEN%{cookbooks}#NORMAL"