Mount /etc/haproxy instead of a single file (allows reload)

Closes #675 (carried with attribution)

haproxy/content.md

@@ -46,9 +46,11 @@ You may need to publish the ports your haproxy is listening on to the host by sp
 ## Directly via bind mount
 
 ```console
-$ docker run -d --name my-running-haproxy -v /path/to/haproxy.cfg:/usr/local/etc/haproxy/haproxy.cfg:ro haproxy:1.7
+$ docker run -d --name my-running-haproxy -v /path/to/etc/haproxy:/usr/local/etc/haproxy:ro haproxy:1.7
 ```
 
+Note that your host's `/path/to/etc/haproxy` folder should be populated with a file named `haproxy.cfg`. If this configuration file refers to any other files within that folder then you should ensure that they also exist (e.g. template files such as `400.http`, `404.http`, and so forth). However, many minimal configurations do not require any supporting files.
+
 ### Reloading config
 
 If you used a bind mount for the config and have edited your `haproxy.cfg` file, you can use haproxy's graceful reload feature by sending a `SIGHUP` to the container: