Allow Custom SSL-Certificates

[Moon93]

I suggest to add a command-line option to allow setting a custom SSL-certificate.
ssl_context can be set with a touple of (certificate.pem, key.pem).
When using Let's Encrypt you are provided with fullchain.pem and privkey.pem.
I suggest a command-line option like this:
updog --ssl-cert fullchain.pem --ssl-key privkey.pem

[patrickhener]

This one can do it: https://github.com/patrickhener/goshs

[bandrel]

Just modify main.py

   ssl_context = None
    if args.ssl:
        #ssl_context = 'adhoc'
        ssl_context=('/etc/letsencrypt/live/domain.com/cert.pem',
                     '/etc/letsencrypt/live/domain.com/privkey.pem')

[felmoltor]

I opened a pull request for this feature here: #67