Support client cert passwords, new TLS options (#118)

Support client cert passwords, new TLS options (#118)

* Support client cert passwords, new TLS options

* Update test_config.py

* Switch to try-except for post_handshake_auth=True

SSLContext.post_handshake_auth raises AttributeError if the property is available but cannot be written to (needs OpenSSL 1.1.1+)

* Also try-except for hostname_checks_common_name=False

* Custom implementation of trustme.CA() that emits encrypted PKs

* lint

* Split name of test

* Updates from review comments

* Don't load default CAs yet