Improve |mach test|.
Improve |mach test|.

Make mach test work with wpt tests.
Allow specifying specific testsuites on the command line
Allow specifying paths to CSS tests on the command line

steveklabnik/servo,szeged/servo,larsbergstrom/servo,upsuper/servo,brendandahl/servo,steveklabnik/servo,pgonda/servo,canaltinova/servo,avadacatavra/servo,peterjoel/servo,A-deLuna/servo,anthgur/servo,akosel/servo,pyfisch/servo,rnestler/servo,jlegendary/servo,dsandeephegde/servo,bjwbell/servo,vks/servo,nerith/servo,pyfisch/servo,caldwell/servo,eddyb/servo,canaltinova/servo,CJ8664/servo,nick-thompson/servo,SimonSapin/servo,nnethercote/servo,nerith/servo,saratang/servo,meh/servo,saneyuki/servo,dvberkel/servo,pgonda/servo,RenaudParis/servo,tafia/servo,splav/servo,akosel/servo,pyfisch/servo,paulrouget/servo,saratang/servo,saneyuki/servo,peterjoel/servo,tempbottle/servo,thiagopnts/servo,upsuper/servo,paulrouget/servo,nick-thompson/servo,nnethercote/servo,pyfisch/servo,emilio/servo,tempbottle/servo,jimberlage/servo,emilio/servo,sadmansk/servo,dagnir/servo,brendandahl/servo,aidanhs/servo,dagnir/servo,nick-thompson/servo,caldwell/servo,mt2d2/servo,A-deLuna/servo,larsbergstrom/servo,dvberkel/servo,jlegendary/servo,tafia/servo,DominoTree/servo,jdramani/servo,mdibaiee/servo,avadacatavra/servo,sadmansk/servo,A-deLuna/servo,nrc/servo,dhananjay92/servo,mbrubeck/servo,jdramani/servo,cbrewster/servo,emilio/servo,kindersung/servo,WriterOfAlicrow/servo,nrc/servo,CJ8664/servo,saratang/servo,pyfisch/servo,saneyuki/servo,RenaudParis/servo,rentongzhang/servo,pyecs/servo,ryancanhelpyou/servo,tschneidereit/servo,sadmansk/servo,thiagopnts/servo,dagnir/servo,meh/servo,rnestler/servo,mt2d2/servo,splav/servo,tafia/servo,ConnorGBrewster/servo,mt2d2/servo,jimberlage/servo,mt2d2/servo,peterjoel/servo,aweinstock314/servo,emilio/servo,youprofit/servo,rnestler/servo,DominoTree/servo,mattnenterprise/servo,fiji-flo/servo,meh/servo,fiji-flo/servo,dati91/servo,notriddle/servo,splav/servo,anthgur/servo,nick-thompson/servo,KiChjang/servo,saneyuki/servo,steveklabnik/servo,aweinstock314/servo,dvberkel/servo,tempbottle/servo,aweinstock314/servo,KiChjang/servo,mdibaiee/servo,dvberkel/servo,walac/servo,akosel/servo,huonw/servo,szeged/servo,wartman4404/servo,bjwbell/servo,mt2d2/servo,peterjoel/servo,saneyuki/servo,tempbottle/servo,j3parker/servo,ConnorGBrewster/servo,notriddle/servo,ryancanhelpyou/servo,nick-thompson/servo,tempbottle/servo,vks/servo,splav/servo,vks/servo,tafia/servo,zentner-kyle/servo,peterjoel/servo,wartman4404/servo,canaltinova/servo,peterjoel/servo,pyfisch/servo,dati91/servo,dhananjay92/servo,caldwell/servo,deokjinkim/servo,meh/servo,akosel/servo,s142857/servo,splav/servo,SimonSapin/servo,nerith/servo,RenaudParis/servo,nrc/servo,jimberlage/servo,dsandeephegde/servo,nerith/servo,paulrouget/servo,deokjinkim/servo,codemac/servo,s142857/servo,szeged/servo,avadacatavra/servo,rentongzhang/servo,pyfisch/servo,nrc/servo,GyrosOfWar/servo,mbrubeck/servo,karlito40/servo,runarberg/servo,dhananjay92/servo,paulrouget/servo,bjwbell/servo,cbrewster/servo,caldwell/servo,karlito40/servo,pyfisch/servo,eddyb/servo,kindersung/servo,eddyb/servo,nrc/servo,sadmansk/servo,notriddle/servo,saratang/servo,bjwbell/servo,vks/servo,ConnorGBrewster/servo,notriddle/servo,nerith/servo,paulrouget/servo,fiji-flo/servo,notriddle/servo,upsuper/servo,pgonda/servo,dvberkel/servo,splav/servo,nnethercote/servo,akosel/servo,dsandeephegde/servo,jimberlage/servo,canaltinova/servo,larsbergstrom/servo,thiagopnts/servo,huonw/servo,ryancanhelpyou/servo,j3parker/servo,boghison/servo,youprofit/servo,walac/servo,saneyuki/servo,saratang/servo,emilio/servo,thiagopnts/servo,avadacatavra/servo,rnestler/servo,vks/servo,huonw/servo,mdibaiee/servo,ryancanhelpyou/servo,jlegendary/servo,runarberg/servo,walac/servo,pgonda/servo,aidanhs/servo,upsuper/servo,upsuper/servo,SimonSapin/servo,CJ8664/servo,avadacatavra/servo,karlito40/servo,ConnorGBrewster/servo,cbrewster/servo,jimberlage/servo,huonw/servo,boghison/servo,steveklabnik/servo,saneyuki/servo,fiji-flo/servo,sadmansk/servo,dagnir/servo,j3parker/servo,ryancanhelpyou/servo,dhananjay92/servo,fiji-flo/servo,jdramani/servo,WriterOfAlicrow/servo,aweinstock314/servo,upsuper/servo,emilio/servo,codemac/servo,eddyb/servo,nrc/servo,nnethercote/servo,nnethercote/servo,AnthonyBroadCrawford/servo,KiChjang/servo,dagnir/servo,fiji-flo/servo,emilio/servo,AnthonyBroadCrawford/servo,rentongzhang/servo,anthgur/servo,tafia/servo,nrc/servo,rentongzhang/servo,thiagopnts/servo,youprofit/servo,SimonSapin/servo,boghison/servo,AnthonyBroadCrawford/servo,paulrouget/servo,mattnenterprise/servo,zentner-kyle/servo,rentongzhang/servo,GyrosOfWar/servo,tschneidereit/servo,walac/servo,huonw/servo,AnthonyBroadCrawford/servo,CJ8664/servo,youprofit/servo,avadacatavra/servo,tschneidereit/servo,boghison/servo,szeged/servo,WriterOfAlicrow/servo,szeged/servo,wartman4404/servo,vks/servo,mattnenterprise/servo,karlito40/servo,walac/servo,szeged/servo,AnthonyBroadCrawford/servo,dsandeephegde/servo,mbrubeck/servo,meh/servo,g-k/servo,cbrewster/servo,s142857/servo,tschneidereit/servo,mattnenterprise/servo,mbrubeck/servo,mt2d2/servo,meh/servo,sadmansk/servo,canaltinova/servo,ryancanhelpyou/servo,youprofit/servo,tschneidereit/servo,thiagopnts/servo,zentner-kyle/servo,huonw/servo,dhananjay92/servo,tempbottle/servo,g-k/servo,SimonSapin/servo,canaltinova/servo,pyfisch/servo,bjwbell/servo,kindersung/servo,KiChjang/servo,nerith/servo,j3parker/servo,AnthonyBroadCrawford/servo,meh/servo,kindersung/servo,mdibaiee/servo,canaltinova/servo,DominoTree/servo,peterjoel/servo,szeged/servo,pgonda/servo,dati91/servo,pyecs/servo,wartman4404/servo,anthgur/servo,pyecs/servo,youprofit/servo,kindersung/servo,eddyb/servo,DominoTree/servo,upsuper/servo,nick-thompson/servo,anthgur/servo,WriterOfAlicrow/servo,steveklabnik/servo,runarberg/servo,eddyb/servo,pyecs/servo,jimberlage/servo,RenaudParis/servo,dati91/servo,tafia/servo,GyrosOfWar/servo,jimberlage/servo,youprofit/servo,ryancanhelpyou/servo,KiChjang/servo,anthgur/servo,notriddle/servo,dvberkel/servo,ConnorGBrewster/servo,larsbergstrom/servo,zentner-kyle/servo,paulrouget/servo,A-deLuna/servo,karlito40/servo,nerith/servo,larsbergstrom/servo,DominoTree/servo,A-deLuna/servo,dsandeephegde/servo,jdramani/servo,eddyb/servo,pyecs/servo,runarberg/servo,anthgur/servo,huonw/servo,deokjinkim/servo,avadacatavra/servo,saneyuki/servo,dvberkel/servo,zentner-kyle/servo,codemac/servo,mdibaiee/servo,cbrewster/servo,tschneidereit/servo,szeged/servo,mbrubeck/servo,akosel/servo,pgonda/servo,brendandahl/servo,fiji-flo/servo,wartman4404/servo,notriddle/servo,mattnenterprise/servo,jlegendary/servo,sadmansk/servo,nick-thompson/servo,SimonSapin/servo,jlegendary/servo,SimonSapin/servo,splav/servo,splav/servo,GyrosOfWar/servo,peterjoel/servo,bjwbell/servo,pyecs/servo,g-k/servo,aidanhs/servo,aidanhs/servo,szeged/servo,notriddle/servo,rnestler/servo,DominoTree/servo,szeged/servo,larsbergstrom/servo,rnestler/servo,mdibaiee/servo,GyrosOfWar/servo,boghison/servo,anthgur/servo,mbrubeck/servo,s142857/servo,larsbergstrom/servo,brendandahl/servo,wartman4404/servo,mbrubeck/servo,KiChjang/servo,tafia/servo,cbrewster/servo,avadacatavra/servo,rentongzhang/servo,dati91/servo,jimberlage/servo,nnethercote/servo,nnethercote/servo,peterjoel/servo,vks/servo,larsbergstrom/servo,mdibaiee/servo,nnethercote/servo,upsuper/servo,runarberg/servo,aidanhs/servo,DominoTree/servo,mt2d2/servo,brendandahl/servo,A-deLuna/servo,pyfisch/servo,g-k/servo,rnestler/servo,boghison/servo,WriterOfAlicrow/servo,SimonSapin/servo,CJ8664/servo,pyecs/servo,deokjinkim/servo,brendandahl/servo,notriddle/servo,GyrosOfWar/servo,pgonda/servo,eddyb/servo,zentner-kyle/servo,saneyuki/servo,j3parker/servo,KiChjang/servo,AnthonyBroadCrawford/servo,walac/servo,jdramani/servo,caldwell/servo,akosel/servo,saneyuki/servo,thiagopnts/servo,RenaudParis/servo,jdramani/servo,GyrosOfWar/servo,mattnenterprise/servo,jlegendary/servo,g-k/servo,cbrewster/servo,mattnenterprise/servo,karlito40/servo,emilio/servo,s142857/servo,s142857/servo,deokjinkim/servo,RenaudParis/servo,dsandeephegde/servo,brendandahl/servo,ConnorGBrewster/servo,notriddle/servo,dhananjay92/servo,fiji-flo/servo,steveklabnik/servo,nnethercote/servo,cbrewster/servo,codemac/servo,g-k/servo,g-k/servo,dsandeephegde/servo,thiagopnts/servo,paulrouget/servo,WriterOfAlicrow/servo,rnestler/servo,DominoTree/servo,runarberg/servo,caldwell/servo,ConnorGBrewster/servo,wartman4404/servo,sadmansk/servo,dagnir/servo,emilio/servo,deokjinkim/servo,deokjinkim/servo,A-deLuna/servo,zentner-kyle/servo,DominoTree/servo,larsbergstrom/servo,dati91/servo,caldwell/servo,DominoTree/servo,steveklabnik/servo,codemac/servo,KiChjang/servo,j3parker/servo,ConnorGBrewster/servo,jlegendary/servo,boghison/servo,emilio/servo,mattnenterprise/servo,aidanhs/servo,WriterOfAlicrow/servo,walac/servo,aweinstock314/servo,dagnir/servo,codemac/servo,CJ8664/servo,aweinstock314/servo,karlito40/servo,jdramani/servo,kindersung/servo,paulrouget/servo,tschneidereit/servo,CJ8664/servo,kindersung/servo,dhananjay92/servo,dati91/servo,tempbottle/servo,bjwbell/servo,CJ8664/servo,splav/servo,peterjoel/servo,nnethercote/servo,saratang/servo,aidanhs/servo,aweinstock314/servo,splav/servo,dati91/servo,j3parker/servo,KiChjang/servo,rentongzhang/servo,dsandeephegde/servo,runarberg/servo,codemac/servo,saratang/servo,canaltinova/servo,larsbergstrom/servo,RenaudParis/servo,paulrouget/servo,KiChjang/servo,mbrubeck/servo,s142857/servo,jimberlage/servo