preview: set default output to png
preview: set default output to png

Signed-off-by: Vinzent Steinberg <72fdda149f36f4b33dc36ed5d23df8c1c631dae1@gmail.com>
Signed-off-by: Ondrej Certik <b816faa87b7d35274d2e545c5be11ed4376f3ccf@certik.cz>

wanglongqi/sympy,amitjamadagni/sympy,Davidjohnwilson/sympy,MridulS/sympy,beni55/sympy,liangjiaxing/sympy,AunShiLord/sympy,iamutkarshtiwari/sympy,kmacinnis/sympy,madan96/sympy,saurabhjn76/sympy,asm666/sympy,toolforger/sympy,fperez/sympy,postvakje/sympy,Sumith1896/sympy,shikil/sympy,dqnykamp/sympy,farhaanbukhsh/sympy,cccfran/sympy,ga7g08/sympy,meghana1995/sympy,atsao72/sympy,VaibhavAgarwalVA/sympy,jbbskinny/sympy,moble/sympy,wyom/sympy,Gadal/sympy,liangjiaxing/sympy,minrk/sympy,AunShiLord/sympy,Titan-C/sympy,yashsharan/sympy,jerli/sympy,yashsharan/sympy,sunny94/temp,bukzor/sympy,debugger22/sympy,cswiercz/sympy,rahuldan/sympy,Sumith1896/sympy,bukzor/sympy,MechCoder/sympy,moble/sympy,aktech/sympy,shikil/sympy,atsao72/sympy,ga7g08/sympy,MridulS/sympy,lindsayad/sympy,vipulroxx/sympy,lidavidm/sympy,Vishluck/sympy,ahhda/sympy,kaichogami/sympy,shipci/sympy,sahmed95/sympy,chaffra/sympy,shikil/sympy,hrashk/sympy,mcdaniel67/sympy,sahilshekhawat/sympy,sahmed95/sympy,debugger22/sympy,pbrady/sympy,emon10005/sympy,wanglongqi/sympy,rahuldan/sympy,Mitchkoens/sympy,souravsingh/sympy,Gadal/sympy,oliverlee/sympy,jamesblunt/sympy,Arafatk/sympy,mafiya69/sympy,grevutiu-gabriel/sympy,jaimahajan1997/sympy,abloomston/sympy,yukoba/sympy,atreyv/sympy,pernici/sympy,kumarkrishna/sympy,kmacinnis/sympy,postvakje/sympy,hargup/sympy,abloomston/sympy,pbrady/sympy,liangjiaxing/sympy,dqnykamp/sympy,bukzor/sympy,chaffra/sympy,aktech/sympy,Designist/sympy,sahilshekhawat/sympy,lidavidm/sympy,lidavidm/sympy,pbrady/sympy,Titan-C/sympy,yashsharan/sympy,aktech/sympy,hrashk/sympy,Vishluck/sympy,shipci/sympy,sunny94/temp,farhaanbukhsh/sympy,diofant/diofant,kevalds51/sympy,drufat/sympy,hargup/sympy,amitjamadagni/sympy,Designist/sympy,oliverlee/sympy,sunny94/temp,sampadsaha5/sympy,abhiii5459/sympy,ChristinaZografou/sympy,tovrstra/sympy,AkademieOlympia/sympy,drufat/sympy,Curious72/sympy,toolforger/sympy,Davidjohnwilson/sympy,AkademieOlympia/sympy,grevutiu-gabriel/sympy,lindsayad/sympy,madan96/sympy,cswiercz/sympy,pandeyadarsh/sympy,wyom/sympy,ahhda/sympy,garvitr/sympy,asm666/sympy,iamutkarshtiwari/sympy,chaffra/sympy,mafiya69/sympy,maniteja123/sympy,yukoba/sympy,wyom/sympy,Arafatk/sympy,MridulS/sympy,kevalds51/sympy,AkademieOlympia/sympy,meghana1995/sympy,ahhda/sympy,moble/sympy,kumarkrishna/sympy,jbbskinny/sympy,meghana1995/sympy,cswiercz/sympy,skidzo/sympy,grevutiu-gabriel/sympy,Arafatk/sympy,asm666/sympy,mafiya69/sympy,vipulroxx/sympy,kmacinnis/sympy,ChristinaZografou/sympy,Gadal/sympy,rahuldan/sympy,drufat/sympy,farhaanbukhsh/sympy,skidzo/sympy,ga7g08/sympy,flacjacket/sympy,wanglongqi/sympy,Vishluck/sympy,atreyv/sympy,dqnykamp/sympy,Mitchkoens/sympy,Mitchkoens/sympy,skidzo/sympy,Curious72/sympy,yukoba/sympy,sahmed95/sympy,kevalds51/sympy,emon10005/sympy,pandeyadarsh/sympy,kaushik94/sympy,maniteja123/sympy,postvakje/sympy,shipci/sympy,atreyv/sympy,VaibhavAgarwalVA/sympy,souravsingh/sympy,atsao72/sympy,Titan-C/sympy,Designist/sympy,abhiii5459/sympy,kaichogami/sympy,toolforger/sympy,jamesblunt/sympy,jbbskinny/sympy,hrashk/sympy,kumarkrishna/sympy,pandeyadarsh/sympy,Curious72/sympy,srjoglekar246/sympy,Shaswat27/sympy,oliverlee/sympy,Sumith1896/sympy,garvitr/sympy,skirpichev/omg,abloomston/sympy,Davidjohnwilson/sympy,beni55/sympy,madan96/sympy,Shaswat27/sympy,minrk/sympy,abhiii5459/sympy,vipulroxx/sympy,kaushik94/sympy,beni55/sympy,jerli/sympy,cccfran/sympy,souravsingh/sympy,iamutkarshtiwari/sympy,debugger22/sympy,jaimahajan1997/sympy,jamesblunt/sympy,hargup/sympy,saurabhjn76/sympy,cccfran/sympy,VaibhavAgarwalVA/sympy,garvitr/sympy,sampadsaha5/sympy,mattpap/sympy-polys,jaimahajan1997/sympy,kaichogami/sympy,Shaswat27/sympy,sahilshekhawat/sympy,ChristinaZografou/sympy,emon10005/sympy,AunShiLord/sympy,lindsayad/sympy,jerli/sympy,mcdaniel67/sympy,sampadsaha5/sympy,maniteja123/sympy,mcdaniel67/sympy,saurabhjn76/sympy,MechCoder/sympy,kaushik94/sympy,MechCoder/sympy