Add SSL support (as well as merge ifixit-production)

In addition to the previous changes (from ifixit-production), we now support HTTPS.

Now, in the environment configuration you can specify:

```
, ssl: true
, key: '/path/to/key.pem'
, cert: '/path/to/cert.pem'
```

Toggling ```ssl``` will enable and disable ssl regardless of whether key/cert files have been specified.

In anticipation for https being enabled,
this also removes the strict protocol for scripts in a few of the templates
and layout partials (changing from ```http://...``` to ```//...```, as it is
supported in a fair amount of browsers these days).