explain how to pass options to your own handler.

it wasn't clear where the user's handler options should go, after looking at the code and trying this is what I've found, correct me if there's a better way.

README.md

@@ -35,6 +35,23 @@ The dispatch options for a Bullet handler looks as follow:
 Simply define this in your dispatch list and your handler will be
 available and handled by Bullet properly.
 
+The third element in the tuple ([{handler, my_stream}]) will be passed 
+to init/4 as Opts, you can add your own options and get them using
+lists:keyfind, for example if we define our handler as:
+
+``` erlang
+{[<<"path">>, <<"to">>, <<"bullet">>], bullet_handler,
+	[{handler, my_stream}, {channel, "my channel"}]}
+```
+
+you can retrieve the channel value as follows:
+
+``` erlang
+init(_Transport, Req, Opts, _Active) ->
+	{channel, Channel} = lists:keyfind(channel, 1, Opts),
+	{ok, Req, #state{channel=Channel}}.
+```
+
 Cowboy handler
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