fix test description

Author: dougwilson

test/app.listen.js

@@ -31,7 +31,7 @@ describe('app.listen()', function(){
     });
   })
 
-  it('should listened to the requested port', function(done){
+  it('should listen on the requested port', function (done) {
     var expectedResponseBody = 'hello world';
     var server;
     var app = express()