Use a ring channel to avoid blocking write of events (#2082)

* Use a ring channel to avoid blocking write of events

* Add eapache/channels dependency

vendor/github.com/eapache/channels/README.md

@@ -0,0 +1,27 @@
+channels
+========
+
+[![Build Status](https://travis-ci.org/eapache/channels.svg?branch=master)](https://travis-ci.org/eapache/channels)
+[![GoDoc](https://godoc.org/github.com/eapache/channels?status.png)](https://godoc.org/github.com/eapache/channels)
+[![Code of Conduct](https://img.shields.io/badge/code%20of%20conduct-active-blue.svg)](https://eapache.github.io/conduct.html)
+
+A collection of helper functions and special types for working with and
+extending [Go](https://golang.org/)'s existing channels. Due to limitations
+of Go's type system, importing this library directly is often not practical for
+production code. It serves equally well, however, as a reference guide and
+template for implementing many common idioms; if you use it in this way I would
+appreciate the inclusion of some sort of credit in the resulting code.
+
+See https://godoc.org/github.com/eapache/channels for full documentation or
+https://gopkg.in/eapache/channels.v1 for a versioned import path.
+
+Requires Go version 1.1 or later, as certain necessary elements of the `reflect`
+package were not present in 1.0.
+
+Most of the buffered channel types in this package are backed by a very fast
+queue implementation that used to be built into this package but has now been
+extracted into its own package at https://github.com/eapache/queue.
+
+*Note:* Several types in this package provide so-called "infinite" buffers. Be
+very careful using these, as no buffer is truly infinite. If such a buffer
+grows too large your program will run out of memory and crash. Caveat emptor.