Disable parallelism in Makefile
Disable parallelism in Makefile

When MAKEFLAGS=-j2 is set in the environment, `make test-travis` can fail
surprisingly, because targets are executed in parallel.

cgvarela/babel,kellyselden/babel,kedromelon/babel,samwgoldman/babel,casser/babel,johnamiahford/babel,shuhei/babel,jnuine/babel,douglasduteil/babel,thejameskyle/babel,codenamejason/babel,iamchenxin/babel,STRML/babel,spicyj/babel,iamolivinius/babel,drieks/babel,tricknotes/babel,amasad/babel,victorenator/babel,KualiCo/babel,ianmstew/babel,zenparsing/babel,plemarquand/babel,tikotzky/babel,garyjN7/babel,mrtrizer/babel,vjeux/babel,jeffmo/babel,ellbee/babel,victorenator/babel,lastjune/babel,samccone/babel,kaicataldo/babel,cgvarela/babel,ming-codes/babel,PolymerLabs/babel,CrabDude/babel,prathamesh-sonpatki/babel,Jeremy017/babel,michaelficarra/babel,jmm/babel,rektide/babel-repl,ezbreaks/babel,ortutay/babel,mrmayfield/babel,ameyms/babel,1yvT0s/babel,PolymerLabs/babel,vadzim/babel,mgcrea/babel,SaltTeam/babel,abdulsam/babel,rn0/babel,framewr/babel,vipulnsward/babel,pingjiang/babel,nmn/babel,nvivo/babel,paulcbetts/babel,aalluri-navaratan/babel,mayflower/babel,sdiaz/babel,jnuine/babel,codenamejason/babel,gxr1020/babel,babel/babel,codenamejason/babel,nishant8BITS/babel,ysmood/babel,benjamn/babel,prathamesh-sonpatki/babel,steveluscher/babel,jridgewell/babel,andrejkn/babel,koistya/babel,kevinb7/6to5,abdulsam/babel,mrapogee/babel,johnamiahford/babel,framewr/babel,KunGha/babel,megawac/babel,paulcbetts/babel,dariocravero/babel,tikotzky/babel,claudiopro/babel,andrewwilkins/babel,kassens/babel,loganfsmyth/babel,ryankanno/babel,arthurvr/babel,inikulin/babel,drieks/babel,PolymerLabs/babel,tricknotes/babel,sdiaz/babel,koistya/babel,grasuxxxl/babel,greyhwndz/babel,ezbreaks/babel,AgentME/babel,samwgoldman/babel,claudiopro/babel,aalluri-navaratan/babel,Industrial/babel,kevhuang/babel,loganfsmyth/babel,dariocravero/babel,beni55/babel,vjeux/babel,thorikawa/babel,hulkish/babel,jmptrader/babel,guybedford/babel,nvivo/babel,ajcrites/babybel,dustyjewett/babel-plugin-transform-es2015-modules-commonjs-ember,Victorystick/babel,cesarandreu/6to5,zertosh/babel,chicoxyzzy/babel,zenlambda/babel,e-jigsaw/babel,TheAlphaNerd/babel,mrtrizer/babel,KualiCo/babel,Dignifiedquire/babel,michaelficarra/babel,chengky/babel,Jeremy017/babel,mgcrea/babel,sejoker/babel,jmptrader/babel,macressler/babel,Jabher/babel,ccschneidr/babel,hulkish/babel,sethcall/babel,hzoo/babel,hzoo/babel,Skillupco/babel,pixeldrew/babel,james4388/babel,kaicataldo/babel,aalluri-navaratan/babel,iamstarkov/babel,cesarandreu/6to5,forivall-old-repos/tacoscript-babel-shared-history,plemarquand/babel,forivall/babel,grasuxxxl/babel,jnuine/babel,zenlambda/babel,cartermarino/babel,lxe/babel,hryniu555/babel,steveluscher/babel,Mark-Simulacrum/babel,claudiopro/babel,Skillupco/babel,VukDukic/babel,steveluscher/babel,hzoo/babel,paulcbetts/babel,ming-codes/babel,mrmayfield/babel,krasimir/babel,cartermarino/babel,Skillupco/babel,jackmew/babel,zjmiller/babel,spicyj/babel,zertosh/babel,sethcall/babel,hryniu555/babel,mgcrea/babel,koistya/babel,hulkish/babel,TheAlphaNerd/babel,cgvarela/babel,grasuxxxl/babel,andrewwilkins/babel,kedromelon/babel,samccone/babel,megawac/babel,garyjN7/babel,macressler/babel,iamchenxin/babel,vipulnsward/babel,zorosteven/babel,thorikawa/babel,nmn/babel,amasad/babel,thorikawa/babel,KunGha/babel,mcanthony/babel,ywo/babel,chicoxyzzy/babel,STRML/babel,TheAlphaNerd/babel,zorosteven/babel,forivall/babel,megawac/babel,greyhwndz/babel,james4388/babel,rektide/babel-repl,samwgoldman/babel,sairion/babel,jeffmo/babel,ryankanno/babel,arthurvr/babel,kevinb7/6to5,kevhuang/babel,moander/babel,pingjiang/babel,iamolivinius/babel,kellyselden/babel,rn0/babel,macressler/babel,jhen0409/babel,sejoker/babel,drieks/babel,andrewwilkins/babel,antn/babel,e-jigsaw/babel,dariocravero/babel,douglasduteil/babel,zorosteven/babel,iamchenxin/babel,hzoo/babel,chicoxyzzy/babel,casser/babel,pixeldrew/babel,lastjune/babel,cesarandreu/6to5,DmitrySoshnikov/babel,ErikBaath/babel,chengky/babel,mcanthony/babel,CrocoDillon/babel,Victorystick/babel,azu/babel,iamolivinius/babel,iamstarkov/babel,ianmstew/babel,kaicataldo/babel,jackmew/babel,guybedford/babel,ellbee/babel,kellyselden/babel,SaltTeam/babel,guybedford/babel,existentialism/babel,rmacklin/babel,kaicataldo/babel,KualiCo/babel,moander/babel,AgentME/babel,jchip/babel,ajcrites/babybel,mrapogee/babel,maurobringolf/babel,vjeux/babel,manukall/babel,bcoe/babel,ezbreaks/babel,zenlambda/babel,babel/babel,victorenator/babel,shuhei/babel,sejoker/babel,krasimir/babel,SaltTeam/babel,sethcall/babel,lastjune/babel,mcanthony/babel,kassens/babel,existentialism/babel,Industrial/babel,manukall/babel,sairion/babel,gxr1020/babel,douglasduteil/babel,amasad/babel,michaelficarra/babel,hubli/babel,Mark-Simulacrum/babel,mrapogee/babel,Dignifiedquire/babel,vadzim/babel,dekelcohen/babel,e-jigsaw/babel,cartermarino/babel,babel/babel,greyhwndz/babel,ajcrites/babybel,james4388/babel,kpdecker/babel,antn/babel,abdulsam/babel,VukDukic/babel,ryankanno/babel,andrejkn/babel,Jabher/babel,ming-codes/babel,dekelcohen/babel,1yvT0s/babel,vhf/babel,jmm/babel,rmacklin/babel,chicoxyzzy/babel,framewr/babel,forivall/babel,ortutay/babel,prathamesh-sonpatki/babel,ramoslin02/babel,beni55/babel,hulkish/babel,ErikBaath/babel,inikulin/babel,bcoe/babel,jackmew/babel,Jeremy017/babel,VukDukic/babel,tricknotes/babel,moander/babel,johnamiahford/babel,nishant8BITS/babel,existentialism/babel,benjamn/babel,jmptrader/babel,kevhuang/babel,CrabDude/babel,Victorystick/babel,loganfsmyth/babel,manukall/babel,jridgewell/babel,jeffmo/babel,kedromelon/babel,shuhei/babel,fabiomcosta/babel,Mark-Simulacrum/babel,thejameskyle/babel,mayflower/babel,chengky/babel,jhen0409/babel,Skillupco/babel,ysmood/babel,ywo/babel,jridgewell/babel,1yvT0s/babel,ortutay/babel,ramoslin02/babel,ysmood/babel,sairion/babel,jridgewell/babel,andrejkn/babel,ameyms/babel,CrabDude/babel,hubli/babel,lxe/babel,pixeldrew/babel,ianmstew/babel,beni55/babel,babel/babel,Dignifiedquire/babel,spicyj/babel,hubli/babel,mayflower/babel,kpdecker/babel,maurobringolf/babel,azu/babel,plemarquand/babel,nmn/babel,fabiomcosta/babel,vipulnsward/babel,kellyselden/babel,zenparsing/babel,ramoslin02/babel,forivall-old-repos/tacoscript-babel-shared-history,inikulin/babel,DmitrySoshnikov/babel,vhf/babel,ccschneidr/babel,ywo/babel,ErikBaath/babel,pingjiang/babel,maurobringolf/babel,jchip/babel,zjmiller/babel,gxr1020/babel,CrocoDillon/babel,rn0/babel