Update server.js (Https doesn't start on specified port)

Hello, 

Very nice piece of code, and so very useful.
Test it for few days now, and answer perfectly my need.

A little correction because of https_port config was not use correctly, and so create a Error: listen EADDRINUSE
if the http is enabled.


I stay tune on the github for new advice, pull request, bugs. 

Several things to test with https, https between node and npm-lazy-mirrror seems to be useful. Friday test seems to be not concluant.

Lucas