wsgi.py: add credit to flask snippet, add docstring

connexion/wsgi.py

@@ -1,4 +1,27 @@
+# adapted from http://flask.pocoo.org/snippets/35/
+
+
 class ReverseProxied(object):
+    '''Wrap the application in this middleware and configure the
+    reverse proxy to add these headers, to let you quietly bind
+    this to a URL other than / and to an HTTP scheme that is
+    different than what is used locally.
+
+    In nginx:
+
+    location /proxied {
+        proxy_pass http://192.168.0.1:5001;
+        proxy_set_header Host $host;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Scheme $scheme;
+        proxy_set_header X-Script-Name /proxied;
+    }
+
+    :param app: the WSGI application
+    :param script_name: override the default script name (path)
+    :param scheme: override the default scheme
+    :param server: override the default server
+    '''
 
     def __init__(self, app, script_name=None, scheme=None, server=None):
         self.app = app