add default icon to config
add default icon to config

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