rack/rack — pull request #292 by angdraug (2011-12-26 14:00:29+00:00)
Title: honor HTTP_X_FORWARDED_SCHEME in Rack#scheme

This makes Rack play nice with the following Nginx line:

```nginx
proxy_set_header X-Forwarded-Scheme $scheme;
```

which is more flexible than a hardwired

```nginx
proxy_set_header X-Forwarded-Ssl on;
```