shallow_clone: true to shave off CI time
shallow_clone: true to shave off CI time

http://blog.appveyor.com/2014/06/04/shallow-clone-for-git-repositories/

Means we don't have to download all those old CefSharp 1 and 3.27 + 3.29 binaries
haozhouxu/CefSharp,zhangjingpu/CefSharp,rover886/CefSharp,battewr/CefSharp,yoder/CefSharp,wangzheng888520/CefSharp,rlmcneary2/CefSharp,twxstar/CefSharp,joshvera/CefSharp,illfang/CefSharp,yoder/CefSharp,windygu/CefSharp,AJDev77/CefSharp,dga711/CefSharp,ITGlobal/CefSharp,rover886/CefSharp,NumbersInternational/CefSharp,jamespearce2006/CefSharp,zhangjingpu/CefSharp,battewr/CefSharp,windygu/CefSharp,rover886/CefSharp,illfang/CefSharp,Octopus-ITSM/CefSharp,jamespearce2006/CefSharp,windygu/CefSharp,VioletLife/CefSharp,gregmartinhtc/CefSharp,ruisebastiao/CefSharp,wangzheng888520/CefSharp,Haraguroicha/CefSharp,ruisebastiao/CefSharp,VioletLife/CefSharp,rover886/CefSharp,yoder/CefSharp,joshvera/CefSharp,Livit/CefSharp,haozhouxu/CefSharp,dga711/CefSharp,Haraguroicha/CefSharp,Livit/CefSharp,AJDev77/CefSharp,NumbersInternational/CefSharp,yoder/CefSharp,NumbersInternational/CefSharp,gregmartinhtc/CefSharp,rlmcneary2/CefSharp,ITGlobal/CefSharp,jamespearce2006/CefSharp,dga711/CefSharp,joshvera/CefSharp,battewr/CefSharp,rlmcneary2/CefSharp,Haraguroicha/CefSharp,Livit/CefSharp,wangzheng888520/CefSharp,Haraguroicha/CefSharp,AJDev77/CefSharp,illfang/CefSharp,gregmartinhtc/CefSharp,ITGlobal/CefSharp,Livit/CefSharp,rover886/CefSharp,AJDev77/CefSharp,VioletLife/CefSharp,windygu/CefSharp,twxstar/CefSharp,ruisebastiao/CefSharp,wangzheng888520/CefSharp,dga711/CefSharp,VioletLife/CefSharp,zhangjingpu/CefSharp,Octopus-ITSM/CefSharp,rlmcneary2/CefSharp,jamespearce2006/CefSharp,Octopus-ITSM/CefSharp,twxstar/CefSharp,Octopus-ITSM/CefSharp,battewr/CefSharp,jamespearce2006/CefSharp,haozhouxu/CefSharp,zhangjingpu/CefSharp,ruisebastiao/CefSharp,haozhouxu/CefSharp,joshvera/CefSharp,gregmartinhtc/CefSharp,Haraguroicha/CefSharp,ITGlobal/CefSharp,NumbersInternational/CefSharp,twxstar/CefSharp,illfang/CefSharp