switch travis build badge in readme to only be of the master branch
switch travis build badge in readme to only be of the master branch

maurobringolf/babel,STRML/babel,kpdecker/babel,kassens/babel,zjmiller/babel,lxe/babel,Skillupco/babel,jchip/babel,iamstarkov/babel,vhf/babel,vhf/babel,hzoo/babel,drieks/babel,drieks/babel,shuhei/babel,fabiomcosta/babel,benjamn/babel,kaicataldo/babel,babel/babel,kaicataldo/babel,ameyms/babel,PolymerLabs/babel,guybedford/babel,kaicataldo/babel,garyjN7/babel,hzoo/babel,kellyselden/babel,dekelcohen/babel,drieks/babel,PolymerLabs/babel,guybedford/babel,chicoxyzzy/babel,krasimir/babel,claudiopro/babel,babel/babel,fabiomcosta/babel,maurobringolf/babel,kedromelon/babel,jridgewell/babel,existentialism/babel,KunGha/babel,hulkish/babel,PolymerLabs/babel,ccschneidr/babel,shuhei/babel,mrtrizer/babel,bcoe/babel,existentialism/babel,babel/babel,vadzim/babel,antn/babel,chicoxyzzy/babel,samwgoldman/babel,hzoo/babel,hulkish/babel,jchip/babel,AgentME/babel,dustyjewett/babel-plugin-transform-es2015-modules-commonjs-ember,benjamn/babel,iamchenxin/babel,kellyselden/babel,kellyselden/babel,AgentME/babel,CrocoDillon/babel,Skillupco/babel,hzoo/babel,zenparsing/babel,mrtrizer/babel,bcoe/babel,dekelcohen/babel,STRML/babel,ameyms/babel,maurobringolf/babel,ccschneidr/babel,existentialism/babel,DmitrySoshnikov/babel,Industrial/babel,tikotzky/babel,chicoxyzzy/babel,Skillupco/babel,Industrial/babel,hulkish/babel,vadzim/babel,lxe/babel,Skillupco/babel,tikotzky/babel,babel/babel,kedromelon/babel,kedromelon/babel,hulkish/babel,garyjN7/babel,iamstarkov/babel,shuhei/babel,guybedford/babel,antn/babel,DmitrySoshnikov/babel,kpdecker/babel,zertosh/babel,jridgewell/babel,kaicataldo/babel,claudiopro/babel,zjmiller/babel,rmacklin/babel,zertosh/babel,kellyselden/babel,iamchenxin/babel,samwgoldman/babel,kassens/babel,claudiopro/babel,jhen0409/babel,jhen0409/babel,samwgoldman/babel,zenparsing/babel,jridgewell/babel,KunGha/babel,chicoxyzzy/babel,CrocoDillon/babel,krasimir/babel,jridgewell/babel,rmacklin/babel,iamchenxin/babel