Document kafka topic's usage
Document kafka topic's usage

Closes #17

nikitamarchenko/open-kilda,telstra/open-kilda,jonvestal/open-kilda,jonvestal/open-kilda,nikitamarchenko/open-kilda,telstra/open-kilda,jonvestal/open-kilda,telstra/open-kilda,carmine/open-kilda,nikitamarchenko/open-kilda,carmine/open-kilda,nikitamarchenko/open-kilda,carmine/open-kilda,carmine/open-kilda,nikitamarchenko/open-kilda,telstra/open-kilda,jonvestal/open-kilda,jonvestal/open-kilda,nikitamarchenko/open-kilda,telstra/open-kilda,telstra/open-kilda,carmine/open-kilda,telstra/open-kilda,carmine/open-kilda