Bump Rack to 1.5.x, but not 1.6 since it doesn't work on 1.8.7: https://travis-ci.org/sinatra/sinatra/jobs/67398284#L155
Bump Rack to 1.5.x, but not 1.6 since it doesn't work on 1.8.7:
https://travis-ci.org/sinatra/sinatra/jobs/67398284#L155

/cc #1009

lastcat/sinatra,kyontan/sinatra,burningTyger/sinatra,mwpastore/sinatra,miyazawatomoka/sinatra,frechei/sinatra,jkowens/sinatra,ryanshaw/sinatra,JonMidhir/sinatra,Wirachmat/sinatra,eileencodes/sinatra,kyontan/sinatra,sinatra/sinatra,nju520/sinatra,QLGu/sinatra,kumji/sinatra,Rayheng/sinatra,gferguson-gd/sinatra,midorineko/sinatra,ryanshaw/sinatra,frechei/sinatra,defsprite/sinatra,siberianbear/sinatra,sethuster/sinatra,JonMidhir/sinatra,miyazawatomoka/sinatra,d-bot/sinatra,d-bot/sinatra,JonRowe/sinatra,laplaceliu/sinatra,kumji/sinatra,sethuster/sinatra,emiliocorpus/sinatra,Rayheng/sinatra,ksw2599/sinatra,cyberid41/sinatra,JonRowe/sinatra,QLGu/sinatra,eileencodes/sinatra,guidohcosta/sinatra,JonMidhir/sinatra,DoraALin/sinatra,Wirachmat/sinatra,jkowens/sinatra,ABaldwinHunter/sinatra-classic,laplaceliu/sinatra,cyberid41/sinatra,mwpastore/sinatra,DoraALin/sinatra,trexnix/sinatra,ganmacs/sinatra,ganmacs/sinatra,guidohcosta/sinatra,porras/sinatra,nicoayala/sinatra,howtolearntocode/sinatra,burningTyger/sinatra,trexnix/sinatra,wzheng1/sinatra,RosenDimov/sinatra,porras/sinatra,ktw1222/sinatra,defsprite/sinatra,lastcat/sinatra,ktw1222/sinatra,sinatra/sinatra,mwpastore/sinatra,ABaldwinHunter/sinatra-classic,nicoayala/sinatra,autopp/sinatra,jenalgit/sinatra,ksw2599/sinatra,emiliocorpus/sinatra,jkowens/sinatra,midorineko/sinatra,howtolearntocode/sinatra,burningTyger/sinatra,dariubs/sinatra,autopp/sinatra,jenalgit/sinatra,dariubs/sinatra,gferguson-gd/sinatra,RosenDimov/sinatra,nju520/sinatra,siberianbear/sinatra,wzheng1/sinatra