Adding release notes and tagging docs for 2.4.0 release

Change-Id: Ic037678de1ad29a9026d2506048b9d3cd38b4494
diff --git a/VERSION b/VERSION
index a724a9c..197c4d5 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.4.0-dev
+2.4.0