Switch travis to xcode 9.3
Switch travis to xcode 9.3

Hammerspoon/hammerspoon,Hammerspoon/hammerspoon,CommandPost/CommandPost-App,latenitefilms/hammerspoon,cmsj/hammerspoon,Habbie/hammerspoon,latenitefilms/hammerspoon,asmagill/hammerspoon,CommandPost/CommandPost-App,CommandPost/CommandPost-App,Hammerspoon/hammerspoon,latenitefilms/hammerspoon,latenitefilms/hammerspoon,Habbie/hammerspoon,CommandPost/CommandPost-App,Habbie/hammerspoon,asmagill/hammerspoon,CommandPost/CommandPost-App,cmsj/hammerspoon,cmsj/hammerspoon,asmagill/hammerspoon,Hammerspoon/hammerspoon,Hammerspoon/hammerspoon,asmagill/hammerspoon,asmagill/hammerspoon,Hammerspoon/hammerspoon,cmsj/hammerspoon,Habbie/hammerspoon,latenitefilms/hammerspoon,cmsj/hammerspoon,latenitefilms/hammerspoon,CommandPost/CommandPost-App,cmsj/hammerspoon,Habbie/hammerspoon,Habbie/hammerspoon,asmagill/hammerspoon