add note about shotgun

README.rdoc

@@ -846,7 +846,7 @@ Note that the streaming behavior, especially the number of concurrent request,
 highly depends on the web server used to serve the application. Some servers,
 like WEBRick, might not even support streaming at all. If the server does not
 support streaming, the body will be sent all at once after the block passed to
-+stream+ finished executing.
++stream+ finished executing. Streaming does not work at all with Shotgun.
 
 If the optional parameter is set to +keep_open+, it will not call +close+ on
 the stream object, allowing you to close it at any later point in the