Fix RabbitMQ version

This library is not only compatible with RabbitMQ 4.0, but with newer RabbitMQ versions such as 4.1 as well.

Author: ansd

README.md

@@ -1,6 +1,6 @@
 # RabbitMQ AMQP 1.0 JavaScript Client
 
-This library is meant to be used with RabbitMQ 4.0. </br>
+This library is meant to be used with RabbitMQ `4.x`. </br>
 Suitable for testing in pre-production environments. The public API(s) could change.
 
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