Support for fail_if_no_peer_cert SSL server option.

[ghost]

SSL option verify alone does not gives full security. Client could send empty certificate and happily access your inner API.

[essen]

Options in alphabetical order please.

[ghost]

OK, I'll do.
But, in the first place, is ranch:filter_options really needed in ranch_ssl:listen?
Why not pass all Opts directly to ssl:listen?
All ssl server options are well known and documented: http://www.erlang.org/doc/man/ssl.html.
When passing unsupported option programmer will get nice and clear exception exit: badarg.
Is there ssl server option undesirable/unsupported by ranch?

[essen]

Please squash the commits into one and I will merge it.