Add missing SSL options key

The Typhoeus adapter provides the ability for users to [pass in a client certificate password](https://github.com/typhoeus/typhoeus/pull/317) along with other SSL options. This patch allows that value to be passed through from Faraday to the adapter.

Without this, [the adapter is busted](https://github.com/typhoeus/typhoeus/issues/346) when used with 0.9.0.

See also:
* https://github.com/lostisland/faraday/issues/333