[docs] add contributors to readme
[docs] add contributors to readme

pauloconnor/sensu,upfluence/sensu,m4ce/sensu,portertech/sensu,quodlibetor/sensu,sensu/sensu,npe9/sensu,javrasya/sensu,yonglehou/sensu,cread/sensu,withnale/sensu,keymone/sensu,disqus/sensu,roobert/sensu,rbramwell/sensu,bf4/sensu,disqus/sensu,somic/sensu,crewton/sensu,solarkennedy/sensu,miyakawataku/sensu,zuazo-forks/sensu,Tapjoy/sensu-mirror