Add config option to force redirect to HTTPS

Replace: https://github.com/hipache/hipache/pull/161

Please, let me know how to add a (functional) test case for such a feature. I'd like to setup a new server with a new configuration file, so that it won't affect existing test cases.
I don't think there is much value in strict comparing this.
On the contrary, I tend to think that people expect these to act the same:

 * `forceHttps: true`
 * `forceHttps: "true"`
 * `forceHttps: "pleaseForceHttps"`

A simple coerce should work:

`httpServer = http.createServer(config.server.forceHttps ? forceHttpsHandler  : httpRequestHandler);`