update requirements.txt
update requirements.txt

michaelMinar/limbo,NUKnightLab/slask,signalnine/alanabot,kylemsguy/limbo,llimllib/limbo,uilab-github/slask,mmisiewicz/slask,dorian1453/limbo,TetraEtc/limbo,freshbooks/limbo,palachu/sdbot,ruhee/limbo,TetraEtc/limbo,uilab-github/slask,llimllib/limbo,shawnsi/limbo,Marclass/limbo,rizaon/limbo,sentinelleader/limbo,UnILabKAIST/slask,wmv/slackbot-python,serverdensity/sdbot