Travis: test against node 6
Travis: test against node 6

Closes #11748

thehogfather/brackets,adobe/brackets,pratts/brackets,Real-Currents/brackets,albertinad/brackets,busykai/brackets,uwsd/brackets,adobe/brackets,Wikunia/brackets,ficristo/brackets,sprintr/brackets,zaggino/brackets-electron,albertinad/brackets,Real-Currents/brackets,Wikunia/brackets,petetnt/brackets,Real-Currents/brackets,rlugojr/brackets,sprintr/brackets,MarcelGerber/brackets,MarcelGerber/brackets,Real-Currents/brackets,thehogfather/brackets,busykai/brackets,petetnt/brackets,rlugojr/brackets,Real-Currents/brackets,Wikunia/brackets,petetnt/brackets,sprintr/brackets,thehogfather/brackets,pratts/brackets,petetnt/brackets,busykai/brackets,zaggino/brackets-electron,uwsd/brackets,busykai/brackets,uwsd/brackets,rlugojr/brackets,adobe/brackets,uwsd/brackets,uwsd/brackets,zaggino/brackets-electron,albertinad/brackets,albertinad/brackets,MarcelGerber/brackets,zaggino/brackets-electron,rlugojr/brackets,Wikunia/brackets,thehogfather/brackets,adobe/brackets,rlugojr/brackets,ficristo/brackets,albertinad/brackets,Wikunia/brackets,adobe/brackets,sprintr/brackets,petetnt/brackets,sprintr/brackets,pratts/brackets,busykai/brackets,ficristo/brackets,pratts/brackets,pratts/brackets,MarcelGerber/brackets,ficristo/brackets,MarcelGerber/brackets,ficristo/brackets,zaggino/brackets-electron,zaggino/brackets-electron,Real-Currents/brackets,thehogfather/brackets