Update badges in README to use Shields
Update badges in README to use Shields

http://shields.io/ provides many standardized badges for OSS. The PNG versions are similar to the images currently used, but the SVG versions added here are more legible on high pixel density displays.

chef/bundler,EthanK28/bundler,haocafes/bundler,zhangkuaiji/bundler,jasonkarns/bundler,masarakki/bundler,RochesterinNYC/bundler,h4ck3rm1k3/bundler,Teino1978-Corp/Teino1978-Corp-bundler,masarakki/bundler,lmtim/bundler,mattbrictson/bundler-1,neslom/bundler,EthanK28/bundler,suhastech/bundler,asymmetric/bundler,ligi/bundler,chef/bundler,seanlinsley/bundler,ngpestelos/bundler,mvz/bundler,nju520/bundler,agis-/bundler,Elffers/bundler,robinboening/bundler,chulkilee/bundler,dilumnavanjana/bundler,kohgpat/bundler,agis-/bundler,jasonkarns/bundler,PG-kura/bundler,Elffers/bundler,elovelan/bundler,jingweno/bundler,christer155/bundler,ximus/bundler,1337807/bundler,Wirachmat/bundler,cstrahan/bundler,dilumnavanjana/bundler,h4ck3rm1k3/bundler,PG-kura/bundler,mpapis/bundler,neslom/bundler,mvz/bundler,ngpestelos/bundler,anil826/bundler,JuanitoFatas/bundler,Eric-Guo/bundler,mdorrance/bundler,ligi/bundler,patvice/bundler,cdwort/bundler,pjump/bundler,ipmobiletech/bundler,bundler/bundler,joshsoftware/bundler,mpapis/bundler,danimashu/bundler,anil826/bundler,EasonYi/bundler,asutoshpalai/bundler,cstrahan/bundler,gregkare/bundler,zhangkuaiji/bundler,vemmaverve/bundler,AiyionPrime/bundler,davydovanton/bundler,RochesterinNYC/bundler,TimMoore/bundler,carpodaster/bundler,Wirachmat/bundler,carpodaster/bundler,danimashu/bundler,mattbrictson/bundler-1,mdorrance/bundler,haonature888/bundler,ipmobiletech/bundler,seanlinsley/bundler,christer155/bundler,CorainChicago/bundler,byroot/bundler,bronzdoc/bundler,schaary/bundler,tgxworld/bundler,simplybusiness/bundler,frsyuki/bundler,wenderjean/bundler,twcctz500000/bundler,Teino1978-Corp/Teino1978-Corp-bundler,tgxworld/bundler,schaary/bundler,simplybusiness/bundler,philnash/bundler,bronzdoc/bundler,gregkare/bundler,cdwort/bundler,TimMoore/bundler,roseweixel/bundler,bundler/bundler,robinboening/bundler,ximus/bundler,suhastech/bundler,chulkilee/bundler,kohgpat/bundler,roseweixel/bundler,jaym/bundler,AiyionPrime/bundler,jingweno/bundler,pivotal-cf-experimental/bundler,smlance/bundler,haonature/bundler,pjump/bundler,steved/bundler,lmtim/bundler,nju520/bundler,elovelan/bundler,jaym/bundler,sideci-sample/sideci-sample-bundler,haonaturel/bundler,frsyuki/bundler,smlance/bundler,pivotal-cf-experimental/bundler,wenderjean/bundler,EasonYi/bundler,asutoshpalai/bundler,asymmetric/bundler,byroot/bundler,CorainChicago/bundler,philnash/bundler,sideci-sample/sideci-sample-bundler,Eric-Guo/bundler,steved/bundler,davydovanton/bundler,patvice/bundler,joshsoftware/bundler,e2/bundler