Update release notes for v0.3.1. (#574)

* Update release notes for v0.3.1.

Signed-off-by: Brian Smith <[email protected]>

* Add PR authorship for non-Buoyant contributors.

Signed-off-by: Brian Smith <[email protected]>

* Wrap lines at 100 characters.

Signed-off-by: Brian Smith <[email protected]>

CHANGES.md

@@ -1,3 +1,28 @@
+## v0.3.1
+
+Conduit 0.3.1 improves Conduit's resilience and transparency.
+
+* Proxy (data plane)
+  * The proxy now makes fewer changes to requests and responses being proxied. In particular,
+    requests and responses without bodies or with empty bodies are better supported.
+  * HTTP/1 requests with different `Host` header fields are no longer sent on the same HTTP/1
+    connection even when those hostnames resolve to the same IP address.
+  * A connection leak during proxying of non-HTTP TCP connections was fixed.
+  * The proxy now handles unavailable services more gracefully by timing out while waiting for an
+    endpoint to become available for the service.
+* Command-line interface
+  * `$KUBECONFIG` with multiple paths is now supported. (PR #482 by @hypnoglow).
+  * `conduit check` now checks for the availability of a Conduit update. (PR #460 by @ahume).
+* Service Discovery
+  * Kubernetes services with type `ExternalName` are now supported.
+* Control Plane
+  * The proxy is injected into the control plane during installation to improve the control plane's
+    resilience and to "dogfood" the proxy.
+  * The control plane is now more resilient regarding networking failures.
+* Documentation
+  * The markdown source for the documentation published at https://conduit.io/docs/ is now open
+    source at https://github.com/runconduit/conduit/tree/master/doc.
+
 ## v0.3.0
 
 Conduit 0.3 focused heavily on production hardening of Conduit's telemetry system. Conduit 0.3