Allow Session#create_channel to accept additional args

In ruby-amqp/bunny#382 and
ruby-amqp/bunny#437 `Session#create_channel` got
some additional arguments. This change allows calling of
`create_channel` with additional arguments.

lib/bunny_mock/session.rb

@@ -88,7 +88,7 @@ def closing?
     #
     # @return [BunnyMock::Channel] Channel instance
     # @api public
-    def create_channel(n = nil, _pool_size = 1)
+    def create_channel(n = nil, _pool_size = 1, *_args)
       # raise same error as {Bunny::Session#create_channel}
       raise ArgumentError, 'channel number 0 is reserved in the protocol and cannot be used' if n && n.zero?