Add support for sway

[Rotekoppen]

Sway is a wayland equivalent to i3.

I did it myself by adding

I3IpcClient.prototype.inputs = function(cb) {
	this.message(100, null, cb);
};

I3IpcClient.prototype.seats = function(cb) {
	this.message(101, null, cb);
};

to index.js

and changing var GET_SOCKET_PATH_CMD = 'i3 --get-socketpath';to var GET_SOCKET_PATH_CMD = 'sway --get-socketpath';