Removed old node engine versions that cannot install npm packages in Travis CI
Removed old node engine versions that cannot install npm packages in Travis CI

GerHobbelt/refluxjs,robert-chiniquy/refluxjs,H3Chief/reflux-core,mjhlybmwq/refluxjs,ericf89/reflux-core,spoike/refluxjs,VanTanev/refluxjs,Sipree/reflux-core,williamle8300/refluxjs,lishengzxc/refluxjs,simonvizzini/refluxjs,juliankrispel/refluxjs,yetone/refluxjs,vebin/refluxjs,StephenGrider/refluxjs,reflux/refluxjs,uniphil/refluxjs,watonyweng/refluxjs,Sipree/refluxjs,VasylHryha/refluxjs,insionng/refluxjs,reflux/reflux-core,sahat/refluxjs,Mayho/refluxjs,taskworld/refluxjs,bsingr/refluxjs,misnet/refluxjs,goatslacker/refluxjs