Readme: Update Python versions to match compile
Readme: Update Python versions to match compile

Also matches recent updates to https://devcenter.heroku.com/articles/python-runtimes
pkumar-appd/python-buildpack,smalleats/heroku-buildpack-python,pmclanahan/heroku-buildpack-python-peep,benmurden/heroku-buildpack-python-ember,ojacobson/heroku-buildpack-python,liyanchang/cloudfoundary-buildbot-buildpack,blazekadam/open2,AltSchool/heroku-buildpack-python,AltSchool/heroku-buildpack-python,driftyco/heroku-buildpack-sphinx,thenovices/heroku-buildpack-scipy,18F/python-buildpack,gitricko/apt-python-buildpack,sjtuadamyang/adamyang-buildpack-python-libjpeg,marcospy/hackathon-globo-app,amanjain/heroku-buildpack-python-with-django-bower,samuelhavron/heroku-buildpack-python,junyoed/heroku-buildpack-python,nwkotto/geodjango-buildpack-with-geos,Nazanin84/python-buildpack,andrespires/python-buildpack,marcospy/hackathon-globo-app,cloudfoundry/python-buildpack,HousekeepLtd/heroku-buildpack-python,soapril/heroku-buildpack-python,dvreed/heroku-buildpack-python-ldap,Stibbons/heroku-buildpack-python-installer,kvarga/heroku-buildpack-python,jvenezia/heroku-buildpack-python,manufacturedba/heroku-buildpack-python,samuelhavron/heroku-buildpack-python,maxcountryman/heroku-buildpack-python,RobertSundling/heroku-buildpack-python-nginx,xica/heroku-buildpack-scipy,igroff/heroku-buildpack-python,samuelhavron/heroku-buildpack-python,ephemerallabs/heroku-buildpack-python,benjaminfox/heroku-buildpack-python-geoip,alexflanagan/operand-buildpack-python,stalnacke/heroku-buildpack-python,heroku/heroku-buildpack-python,jimlindeman/python-buildpack-collectd,skilljar/heroku-buildpack-python,gitricko/apt-python-buildpack,slorg1/heroku-buildpack-python,pkumar-appd/python-buildpack,Nazanin84/python-buildpack,hsr-ba-fs15-dat/heroku-buildpack,miraculixx/heroku-buildpack-python,marcospy/hackathon-globo-app,edmorley/heroku-buildpack-python,rapilabs/heroku-buildpack-python,benjaminfox/heroku-buildpack-python-geoip,PerceptumNL/heroku-buildpack-python,jimlindeman/python-buildpack-collectd,liyanchang/buildbot-master-buildpack,Mause/heroku-buildpack-python,ywarezk/heroku-buildpack-geodjango,pkumar-appd/python-buildpack,cortexintel/heroku-buildpack-scipy,projetoeureka/heroku-buildpack-scipy,ad-m/heroku-buildpack-python,nikita-pivovarov/heroku-buildpack-python-ldap,cloudfoundry/python-buildpack,zakdoek/heroku-buildpack-django,joshisa/python-buildpack,ryanhiebert/heroku-buildpack-python,doda/heroku-buildpack-python,dubsmash/heroku-buildpack-python,lukaszkorecki/heroku-buildpack-python,bobsilverberg/heroku-buildpack-python-peep,joshowen/heroku-buildpack-python,grivescorbett/heroku-buildpack-python,oberlin/heroku-buildpack-python,markine/heroku-buildpack-python,Apogaea/heroku-buildpack-python,pebble/cloudpebble-buildpack,joshisa/python-buildpack,samuelhavron/heroku-buildpack-python,samuelhavron/heroku-buildpack-python,marianzange/heroku-buildpack-python,ruscoder/heroku-buildpack-python,andrespires/python-buildpack,mythmon/heroku-buildpack-python-nodejs,dulaccc/heroku-buildpack-geodjango,vlidholt/heroku-buildpack-scipy,swils/heroku-buildpack-python,agriffis/heroku-buildpack-python,wbrefvem/heroku-buildpack-python,andrespires/python-buildpack,loanzen/heroku-buildpack-python,edenspiekermann-amsterdam/heroku-buildpack-python,cclauss/heroku-buildpack-python,samuelhavron/heroku-buildpack-python,nemesiscodex/heroku-buildpack-python,andela-brotich/wger-buildpack-python,integricho/heroku-buildpack-python-ffmpeg2.1-with-codecs,benmurden/heroku-buildpack-python-ember,tommyvn/heroku-buildpack-python,samuelhavron/heroku-buildpack-python,brianthomas/heroku-buildpack-textmining,papaeye/heroku-buildpack-python-bower,kowito/python-buildpack,pwdel1/heroku-buildpack-scipy,18F/python-buildpack,maciejgryka/heroku-buildpack-spcedge,nadirizr/heroku-buildpack-python-gulp,DylanLukes/heroku-buildpack-python,arnaudlimbourg/heroku-buildpack-python,rbtying/heroku-buildpack-python,WonderThink/heroku-buildpack-python-ffmpeg-geoip,joshisa/python-buildpack,liyanchang/cloudfoundary-buildbot-buildpack,Scalingo/python-buildpack,Tiger66639/buildbot-master-buildpack,gaumire/heroku-buildpack-python,cdht/heroku-buildpack-python,YoApp/heroku-buildpack-python-twemproxy,river-jade/heroku-buildpack-scipy,monological/heroku-buildpack-python-opencv,samuelhavron/heroku-buildpack-python,ianyh/heroku-buildpack-python-bower,icoxfog417/heroku-buildpack-python,doda/heroku-buildpack-python,kowito/python-buildpack,HanSooloo/heroku-buildpack-python,nicktimko/heroku-buildpack-scipy,plangrid/heroku-buildpack-python,zakdoek/heroku-buildpack-django,martingascon/heroku-buildpack-python,buildbot/buildbot-master-buildpack,beni55/heroku-buildpack-python,Brogency/heroku-buildpack-python-gulp,liyanchang/cloudfoundary-buildbot-buildpack,gitricko/apt-python-buildpack,jamarparris/heroku-buildpack-python-swig,marcospy/heroku-buildpack-scipy,predata/heroku-buildpack-scipy,swanson/heroku-buildpack-python-ortools,jimlindeman/python-buildpack-collectd,mobify/heroku-buildpack-python-swig,ad-m/heroku-buildpack-python,TipWander/heroku-buildpack-geodjango,brightforme/heroku-buildpack-python,scrapinghub/scrapinghub-buildpack-scrapy,Scalingo/python-buildpack,Nazanin84/python-buildpack,joshfriend/heroku-buildpack-python,alexflanagan/operand-buildpack-python,cloudfoundry/python-buildpack,adamroth/heroku-buildpack-python-pdftk,18F/python-buildpack,rollokb/heroku-buildpack-python,ekkleesia2/heroku-buildpack-python,wbrefvem/heroku-buildpack-python,resmio/heroku-buildpack-geodjango,heroku/heroku-buildpack-python,kowito/python-buildpack