Remove leading slash from keep-alive request path
Remove leading slash from keep-alive request path

`HEROKU_URL` always has a trailing slash, this fixes a double slash
issue.

markstory/hubot,broccolini/hubot,andrewpong/awp-hubot,will/willbot,bgranberry/hubot,dopeboy/hubot,jasonkarns/hubot,plated/hubot,wyncode/hubot,yyolk/glitchby,kristenmills/hubot,alexchenfeng/hubot,scboucher/hubot,eshamow/gutterbot,mujiansu/hubot,imkmf/bhamruby-hubot,nandub/hubot,alex-zhang/hubot,fgbreel/hubot,jasonrhodes/botzero,armilam/lessonly-bort,julianromera/hubot,poppingtonic/hubot,ooohiroyukiooo/hubot,ClaudeBot/hubot,mchill/hubot,cameronmcefee/hubot,hubotio/hubot,mjurczyk/hubot,voltsdigital/hubot,jaketrent/moneypenny,melexis/melexis-hubot,krahman/hubot,limianwang/hubot,alexchenfeng/hubot,alucardzhou/hubot,mutewinter/hubot,markstory/hubot,PropertyUX/nubot,decaffeinate-examples/hubot,b3nj4m/hubot,SIOPCO/hubot,eetuuuu/hubot,imkmf/bhamruby-hubot,Drooids/hubot,jschell/hubot,rlugojr/hubot,kyleconroy/karmabot,ToriTomyuTomyu/nothing-yet,AlexandrPuryshev/hubot,edorsey/hubot,rileytg/chenbot,ajschex/hubot,aslihandincer/hubot,brodul/hubot,github/hubot,ykusumi/test-hubot,tiagochiavericosta/hubot,WaleedAshraf/hubot,decaffeinate-examples/hubot,ykelvis/hubot,Mattlk13/Hubot,alexchenfeng/hubot,mauricionr/hubot,GrimDerp/hubot,hubotio/hubot,msound/hubot,hotrannam/hubot,keyvanakbary/hubot,yujiroarai/hws-hubot,RiddickSky/hubot,ouadie-lahdioui/hubot,joshsobota/hubot,makii42/hubot,PropertyUX/nubot,nandub/hubot,mcifani/dog-yoda,pchaigno/hubot,mrb/hubot,alexchenfeng/hubot,awbauer/hubot,minted/hubot,doudoupower/hubot,rmdelo/appboy-hubot,yyolk/glitchby,daudich/hubot,bradparks/hubot__github_chat_bot,zvelo/hubot,sdimkov/hubot,shinvdu/hubot,taojuntjpp/hubot,michaelansel/hubot,Arthraim/merlin,blackwellops/hubot,geoffreyanderson/hubot,fstehle/hubot,ddmng/brazil82-hubot,PopExpert/hubot,Snorlock/hubot,davidkassa/hubot,rafaell-lycan/Hubot-X9,andrewpong/awp-hubot,will/willbot,skcript/skubot,ajayanandgit/hubot,cycomachead/hubot,craig5/hubot,danielcompton/hubot,leohmoraes/hubot,github/hubot,nakaearth/myhubot,hcxiong/hubot,lisb/hubot,lukw00/hubot,kgrz/hubot,lisb/hubot,codydaig/hubot,jaketrent/moneypenny,lizardpie/hubot,howprice/hubot,mcifani/dog-yoda,scboucher/hubot,vkhang55/hubot,alexchenfeng/hubot,gregkare/hubot,ToriTomyuTomyu/nothing-yet,PopExpert/hubot,Hartmarken/hubot,wieden-kennedy/hubot,rayatbuzzfeed/hubot,mcanthony/hubot,jianchen2580/hubot,rileytg/chenbot,lisb/hubot,kkirsche/hubot,sharabash/hubot,CobyR/hubot,lizardpie/hubot,chadfurman/hubot,broccolini/hubot,RavenB/hubot,iDTLabssl/hubot