Added Machinery to Messaging section.

Machinery is an asynchronous task queue/job queue based on distributed
message passing. Think of it as Celery for Golang.

So called tasks (or jobs if you like) are executed concurrently either
by many workers on many servers or multiple worker processes on a single
server using Golang's goroutines.

README.md

@@ -428,6 +428,7 @@ See [go-hardware](https://github.com/rakyll/go-hardware) for a comprehensive lis
 * [go-notify](https://github.com/TheCreeper/go-notify) - Native implementation of the freedesktop notification spec.
 * [go-nsq](https://github.com/bitly/go-nsq) - the official Go package for NSQ
 * [gopush-cluster](https://github.com/Terry-Mao/gopush-cluster) - gopush-cluster is a go push server cluster.
+* [machinery](https://github.com/RichardKnop/machinery) - An asynchronous task queue/job queue based on distributed message passing.
 * [NATS](https://github.com/apcera/nats) - A lightweight and highly performant publish-subscribe and distributed queueing messaging system.
 * [oplog](https://github.com/dailymotion/oplog) - A generic oplog/replication system for REST APIs
 * [pubsub](https://github.com/tuxychandru/pubsub) - A simple pubsub package for go.