add debug() for .listen() and .keys=

lib/application.js

@@ -63,6 +63,7 @@ Application.prototype.__proto__ = Emitter.prototype;
  */
 
 app.listen = function(){
+  debug('listen');
   var server = http.createServer(this.callback());
   return server.listen.apply(server, arguments);
 };
@@ -116,6 +117,7 @@ app.callback = function(){
 
 app.__defineSetter__('keys', function(keys){
   var ok = Array.isArray(keys) || keys instanceof Keygrip;
+  debug('keys %j', keys);
   if (!ok) throw new TypeError('app.keys must be an array or Keygrip');
   if (!(keys instanceof Keygrip)) keys = new Keygrip(keys);
   this._keys = keys;