osx icon badge support - setBadgeLabel

[falsecz]

osx is supported only, I'm not sure is there way to implement on other platforms

var gui = require('nw.gui'); 
var win = gui.Window.get();
win.setBadgeLabel("3");

[tommoor]

nice! such a small amount of code too

[rogerwang]

Thanks. Please create another PR to add yourself to AUTHORS.

[hachre]

thanks a lot guys :)