[gemspec] use ruby in gemspec, don't shell out to git
[gemspec] use ruby in gemspec, don't shell out to git

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