Roundcube is not available on Jessie except in backports.  This role is
also out of date and needs reviewed and updated for the release included
in backports.  Roundcube could alternatively be installed from source as
recommended by the maintainers.

See https://wiki.mozilla.org/Security/Server_Side_TLS for details.
Removes RC4 cipher. Fixes issue #341.
Also explicitly disabled SSLCompression and enables OCSP stapling.

We should put all these settings in
/etc/apache2/mods-enabled/ssl.conf
to avoid duplication...