Add a note about Sinatra::Base to the README
Add a note about Sinatra::Base to the README

Edited-By: Ryan Tomayko <d1f05aa9451a08289b556bf689f87072a26bd23a@gmail.com>

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