Update plugins.md
Add Convoy to Docker plugin list.
@@ -37,6 +37,11 @@ The following plugins exist:
environments with features that include tenant isolation, automated
provisioning, encryption, secure deletion, snapshots and QoS.
+* The [Convoy plugin](https://github.com/rancher/convoy) is a volume plugin for a
+ variety of storage back-ends including device mapper and NFS. It's a simple standalone
+ executable written in Go and provides the framework to support vendor-specific extensions
+ such as snapshots, backups and restore.
+
* The [Flocker plugin](https://clusterhq.com/docker-plugin/) is a volume plugin
which provides multi-host portable volumes for Docker, enabling you to run
databases and other stateful containers and move them around across a cluster
