appveyor: Only build official branches
appveyor: Only build official branches

This will make appveyor only do a build for each pull request and not
two (because it builds first the branch and then the PR).

impmihai/coala,FeodorFitsner/coala,meetmangukiya/coala,Asnelchristian/coala,JohnS-01/coala,Tanmay28/coala,ayushin78/coala,coala-analyzer/coala,aptrishu/coala,AbdealiJK/coala,stevemontana1980/coala,coala-analyzer/coala,NalinG/coala,Balaji2198/coala,djkonro/coala,scottbelden/coala,andreimacavei/coala,ManjiriBirajdar/coala,damngamerz/coala,karansingh1559/coala,NalinG/coala,AdeshAtole/coala,sagark123/coala,Uran198/coala,kartikeys98/coala,tltuan/coala,swatilodha/coala,FeodorFitsner/coala,damngamerz/coala,arjunsinghy96/coala,ManjiriBirajdar/coala,ayushin78/coala,CruiseDevice/coala,netman92/coala,arafsheikh/coala,SambitAcharya/coala,yashtrivedi96/coala,sils1297/coala,SambitAcharya/coala,aptrishu/coala,scottbelden/coala,refeed/coala,nemaniarjun/coala,yashtrivedi96/coala,AdeshAtole/coala,coala/coala,yashLadha/coala,sagark123/coala,JohnS-01/coala,Shade5/coala,aptrishu/coala,swatilodha/coala,Tanmay28/coala,NalinG/coala,ManjiriBirajdar/coala,mr-karan/coala,jayvdb/coala,FeodorFitsner/coala,sophiavanvalkenburg/coala,SambitAcharya/coala,tltuan/coala,coala/coala,Nosferatul/coala,impmihai/coala,tltuan/coala,tushar-rishav/coala,MariosPanag/coala,Asalle/coala,refeed/coala,arjunsinghy96/coala,NalinG/coala,karansingh1559/coala,shreyans800755/coala,djkonro/coala,Asalle/coala,AbdealiJK/coala,nemaniarjun/coala,lonewolf07/coala,refeed/coala,NalinG/coala,abhiroyg/coala,dagdaggo/coala,yland/coala,shreyans800755/coala,scriptnull/coala,Tanmay28/coala,stevemontana1980/coala,SambitAcharya/coala,lonewolf07/coala,sudheesh001/coala,arjunsinghy96/coala,Nosferatul/coala,JohnS-01/coala,impmihai/coala,nemaniarjun/coala,jayvdb/coala,ayushin78/coala,incorrectusername/coala,scriptnull/coala,scriptnull/coala,MariosPanag/coala,tushar-rishav/coala,meetmangukiya/coala,yland/coala,NalinG/coala,svsn2117/coala,Tanmay28/coala,AbdealiJK/coala,saurabhiiit/coala,sudheesh001/coala,stevemontana1980/coala,sils1297/coala,Balaji2198/coala,dagdaggo/coala,RJ722/coala,Balaji2198/coala,arafsheikh/coala,yashLadha/coala,rimacone/testing2,vinc456/coala,kartikeys98/coala,RJ722/coala,damngamerz/coala,rresol/coala,abhiroyg/coala,coala/coala,mr-karan/coala,scriptnull/coala,svsn2117/coala,abhiroyg/coala,incorrectusername/coala,Asnelchristian/coala,arafsheikh/coala,d6e/coala,scottbelden/coala,kartikeys98/coala,arush0311/coala,vinc456/coala,arush0311/coala,yland/coala,tushar-rishav/coala,SambitAcharya/coala,dagdaggo/coala,lonewolf07/coala,sophiavanvalkenburg/coala,coala-analyzer/coala,SanketDG/coala,vinc456/coala,Tanmay28/coala,SanketDG/coala,saurabhiiit/coala,CruiseDevice/coala,yashLadha/coala,mr-karan/coala,NiklasMM/coala,Asnelchristian/coala,scriptnull/coala,Asalle/coala,Nosferatul/coala,andreimacavei/coala,rimacone/testing2,sophiavanvalkenburg/coala,sudheesh001/coala,saurabhiiit/coala,MattAllmendinger/coala,NiklasMM/coala,rresol/coala,SambitAcharya/coala,sils1297/coala,arush0311/coala,Shade5/coala,NalinG/coala,svsn2117/coala,andreimacavei/coala,djkonro/coala,SanketDG/coala,d6e/coala,scriptnull/coala,d6e/coala,rresol/coala,Uran198/coala,CruiseDevice/coala,RJ722/coala,MattAllmendinger/coala,sagark123/coala,meetmangukiya/coala,MattAllmendinger/coala,incorrectusername/coala,yashtrivedi96/coala,Shade5/coala,swatilodha/coala,netman92/coala,NiklasMM/coala,MariosPanag/coala,netman92/coala,AdeshAtole/coala,jayvdb/coala,Tanmay28/coala,Tanmay28/coala,Tanmay28/coala,rimacone/testing2,SambitAcharya/coala,Uran198/coala,karansingh1559/coala,shreyans800755/coala,scriptnull/coala