update README about slackbot_settings.py
update README about slackbot_settings.py

hotsyk/slackbot,kave/zenhub-slackbot,kivra/slackbot,s1ider/slackbot,kienpham2000/slackbot,merqurio/slackbot,kave/zenhub-slackbot,foresterh/slackbot,kivra/slackbot,zatonovo/slackbot,s1ider/slackbot,kienpham2000/slackbot,merqurio/slackbot,zatonovo/slackbot,TimZehta/slackbot,jathanism/slackbot,grantvix/images,kenden/slackbot,kenden/slackbot,hotsyk/slackbot,pengzhangdev/slackbot,Haukiii/slackbot,STANAPO/slackbot,TimZehta/slackbot,philfung/slackbot,smalenfant/slackbot,lins05/slackbot,pengzhangdev/slackbot,STANAPO/slackbot,philfung/slackbot,Haukiii/slackbot,foresterh/slackbot,jathanism/slackbot,lins05/slackbot,smalenfant/slackbot