OVERRIDE => override in notify_icon.h
Remove tray_icon_win.h
win: Add NotifyIcon::DisplayBalloon
Add Tray.displayBallon API
win: Add "balloon-clicked" event for Tray
win: Remove XP code in Tray
docs: Tray balloon
win: Add "balloon-show" and "balloon-closed" events
docs: "balloon-show" and "balloon-closed" events
Fix building on Mac
Merge pull request #872 from atom/tray-balloon

Add Tray.displayBalloon API on Windows