Remove OSX from travis
Remove OSX from travis

Builds take too long on free tier

Tyriar/xterm.js,sourcelair/xterm.js,xtermjs/xterm.js,akalipetis/xterm.js,xtermjs/xterm.js,sourcelair/xterm.js,sourcelair/xterm.js,akalipetis/xterm.js,xtermjs/xterm.js,akalipetis/xterm.js,xtermjs/xterm.js,xtermjs/xterm.js,Tyriar/xterm.js,Tyriar/xterm.js,sourcelair/xterm.js,Tyriar/xterm.js,akalipetis/xterm.js,Tyriar/xterm.js