The hyphen is not needed in the configuration. To enable SSL, use a configuration like this:
production:
sessions:
default:
options:
ssl: true
About the available options, the discussion you linked is about an old code. Earlier it was possible to set the SSL certificate in the configuration:
But that code got removed in this commit:
And the Moped version which comes with Mongoid 3 has options only for host and port:
https://github.com/mongoid/moped/blob/1.5.0-stable/lib/moped/sockets/ssl.rb#L12-L29