Add SSL support
Add SSL support

See vklochan/python-logstash#28

Adds initial support for SSL. The implementation supports the following
features:

* Remote certificate validation
* Custom CA bundles
* Client side certs

SSL is now on by default.

koendeschacht/python-logstash-async,loganasherjones/python-logstash-async,eht16/python-logstash-async