Document http2https and https2http

doc-src/features/reverseproxy.html

@@ -7,7 +7,22 @@ mitmproxy forwards HTTP proxy requests to an upstream proxy server.
 <table class="table">
     <tbody>
         <tr>
-            <th width="20%">command-line</th> <td>-R http[s]://hostname[:port]</td>
+            <th width="20%">command-line</th> <td>-R <i>schema</i>://hostname[:port]</td>
         </tr>
     </tbody>
 </table>
+
+Here, **schema** is one of http, https, http2https or https2http. The latter
+two extended schema specifications control the use of HTTP and HTTPS on
+mitmproxy and the upstream server. You can indicate that mitmproxy should use
+HTTP, and the upstream server uses HTTPS like this:
+
+	http2https://hostname:port
+
+And you can indicate that mitmproxy should use HTTPS while the upstream
+service uses HTTP like this:
+
+	https2http://hostname:port
+
+
+

doc-src/features/upstreamproxy.html

@@ -11,3 +11,17 @@ mitmproxy forwards ordinary HTTP requests to an upstream server.
         </tr>
     </tbody>
 </table>
+
+Here, **schema** is one of http, https, http2https or https2http. The latter
+two extended schema specifications control the use of HTTP and HTTPS on
+mitmproxy and the upstream server. You can indicate that mitmproxy should use
+HTTP, and the upstream server uses HTTPS like this:
+
+	http2https://hostname:port
+
+And you can indicate that mitmproxy should use HTTPS while the upstream
+service uses HTTP like this:
+
+	https2http://hostname:port
+
+