Update Changelog and documentation with separate-HA-backend info.

CHANGELOG.md

@@ -1,5 +1,14 @@
 ## 0.5.0 (Unreleased)
 
+FEATURES:
+
+ * **Split Data/High Availability Physical Backends**: You can now configure
+   two separate physical backends: one to be used for High Availability
+   coordination and another to be used for encrypted data storage. See the
+   [configuration
+   documentation](https://vaultproject.io/docs/config/index.html) for details.
+   [GH-395]
+
 IMPROVEMENTS:
 
  * cli: Output secrets sorted by key name [GH-830]

website/source/docs/config/index.html.md

@@ -38,6 +38,11 @@ to specify where the configuration is.
   is stored. There are multiple options available for storage backends,
   and they're documented below.
 
+* `ha_backend` (optional) - Configures the storage backend where Vault HA
+  coordination will take place. Must be an HA-supporting backend using the
+  configuration options as documented below. If not set, HA will be attempted
+  on the backend given in the `backend` parameter.
+
 * `listener` (required) - Configures how Vault is listening for API requests.
   "tcp" is currently the only option available. A full reference for the
    inner syntax is below.