Add plugin handler.
Cowsay and Meetup to use new plugin register.
Stub PluginHandler.plugin in help spec.

Prior to this stub pretty_help was outputting the ascii table
containg every plugin that registered.
Chuck norris plugin to the new plugin registration.
Duck Duck Go to new plugin registration style.
Ferengi Rules to new plugin registration.
Add Github status to new plugin registration style.
Make a sandwich to new plugin registration.
Update reddit joke to use new registration.
Turbot info to new registration.
Remove old help message.
Gem search to new registration style.