SSL Support

First attempt at providing SSL support. However, as things stand now it is impossible to produce configuration like the following:
```
listen foo-listen
  bind :80
  redirect scheme https if !{ ssl_fc }
  bind :443 ssl crt /path/to/cert.crt
  ...
```
It seems awkward to make $ports a hash of [ portnum => ssl ].
limiting ssl to crt only seems… limiting.