message: Add Twitter to README
diff: @@ -16,6 +16,7 @@ to find out more about the origin story and design philosophy of Envoy.
  * [envoy-dev](https://groups.google.com/forum/#!forum/envoy-dev): Envoy developer discussion (APIs,
  feature design, etc.).
  * [#lyft-envoy](http://webchat.freenode.net/?channels=lyft-envoy): IRC (synced to Gitter)
  +* [Twitter](https://twitter.com/EnvoyProxy/): Follow along on Twitter!
  * [lyft/envoy](https://gitter.im/lyft/envoy): Gitter (most people use Gitter)
  ## Reporting security vulnerabilities
  