Move config.yml to config-sample.yml

Signed-off-by: Ben Firshman <ben@firshman.co.uk>
Add support for network passwords

Also renamed `password` to `nickserv_password` and made it optional.

Signed-off-by: Ben Firshman <ben@firshman.co.uk>
Add support for ssl

Set by `ssl: true/false` in config.yml.

Signed-off-by: Ben Firshman <ben@firshman.co.uk>
Improve Dockerfile

 - Remove pip installation because this is now in python image
 - Add only requirements.txt before running pip so it can be
   cached

Signed-off-by: Ben Firshman <ben@firshman.co.uk>