releasenotes: add notes for Mitaka cycle

* drop reno note, which is useless because we had no release before.
* create a new note that summarize what does this new module.

Change-Id: Iec588a64db7d28af365fa580dfe56d282f922d4f

releasenotes/notes/first_release-d4c9a7d326ead137.yaml

@@ -0,0 +1,9 @@
+---
+prelude: >
+  This is the first release of puppet-mistral module.
+
+features:
+  - Allow to deploy Mistral API, Engine and Executor.
+  - Manage Keystone resources for Mistral.
+  - Allow to deploy Mistral API in WSGI with Apache.
+  - Manage Mistral database.

releasenotes/notes/use-reno-1caaec4ba5aa4285.yaml

@@ -1,6 +0,0 @@
----
-prelude: >
-   Release notes are generated by Reno.
-features:
-  - Release notes are no longer maintained by hand, we now use the reno tool to
-    manage them.