Add HTTPS support

[wizcheng]

No description provided.

[cburgmer]

Hey Wiz, thanks a lot for merging back the changes.

I understand you wanted to make both the trust and the key store configurable via the client.

I assume http-kit's client did not offer the option, which is the reason you replaced it? I don't mind the new client, if it provides the same promise of non-blocking calls.

Before we talk about merging, can I ask whether configuring trust and key store via JVM parameters didn't work out for you? I remember configuring it via the JVM directly, similar to what's described here: http://blog.kunicki.org/blog/2015/09/10/ssl-client-certificates-on-the-jvm/.

I'll probably won't have much time the next days, my answer's might be delayed. But I wanted to give you an initial response as quickly as possible now.