Problem: omni_httpd doesn't support SSL

[yrashk]

This is because this was out of the scope of the initial prototype. For any real use, this is necessary.

Ideally, two options are needed:

1. User-supplied certificate (easy, follow what h2o does)
2. ACME (harder, but very good for adoption)

The closer we get to a user experience of Caddy, the better. Local certificate provisioning know-how can be found in smallstep/truststore

[yrashk]

Moved this to the next milestone as this problem can be temporarily mitigated by putting a reverse proxy in front of omni_httpd (which is prudent while omni_httpd is not mature)

[yrashk]

Superseded by #405