Version series 3.6.x of RabbitMQ is being active quite long time, because first version — 3.6.0 — was released on the 20th of October 2015. For more than 2 years this message broker has become better and better product with more and more helpful features or supported languages by client libraries..
Version 3.7.0 was released on the 29th of November 2017. On the December two versions were released: 3.7.1 and 3.7.2, both containing fixes to known issues.
At the end of the October 2017, Michael Klishin wrote on the mailing list about the proposition to close version series 3.6.x by the 1st of May 2018.
You can read about how to install versions 3.7.x under Linux on the tutorial pages:
Complete message can be found here.