[WIP] Add openssl ssl.py bindings (Refs #77)

Have merged https://github.com/pyca/cryptography/pull/245 and https://github.com/pyca/cryptography/pull/241 already.

There is also https://github.com/pyca/cryptography/issues/239 to resolve.

https://github.com/cyli/cryptography/commit/6199b58593cc933d5f59bf39301501a05fcb6bbc  also removes some things that might be necessary for PyOpenSSL (and is at least in https://github.com/exarkun/opentls/blob/b38a0cb646c34fe272fd747d6ec096416e279ef8/tls/c/ssl.py#L285)