Adding an option to launch a HTTPS server

### Adding several options concerning HTTPS:

* -S / --ssl: launch a https server
* -C / --cert: path to cert file (default: cert.pem)
* -K / --key: path to key file (default: key.pem)

The arguments are uppercase not to collide with the current existing one.

The idea behind this pull request is to enable developers to fastly launch a https server for dev purposes (typically when working on Speech Recognition APIs or on code injection within HTTPS pages).

### How to create dummy cert and key files for dev
```bash
openssl genrsa -out key.pem 4096
openssl req -new -key key.pem -out csr.pem -subj "/C=US/ST=California/L=San Francisco/O=Local-Company/OU=dev/CN=localhost/emailAddress=test@test.com"
openssl x509 -req -days 9999 -in csr.pem -signkey key.pem -out cert.pem
rm csr.pem
```

Then go to chrome settings to register your key (advanced settings --> HTTPS/SSL --> Manage Certificates)
Click `Import` and add your cert.pem file to register your development certificate and not be bothered anymore by chrome warnings.

Or use the `--ignore-certificate-errors` option in Chromium if you are in a hurry.