Update README.

Author: zeekay

README.rst

@@ -148,7 +148,7 @@ Advanced Usage
 --------------
 Normally websocket routes happen outside of the normal request context. You can
 get a request context in your websocket handler by using
-`app.request_context`::
+``app.request_context``::
 
     app = Flask(__name__)
     ws = GeventWebSocket(app)