Update CHANGES.txt to reflect version 0.8.0-alpha and expected release
date.
diff --git a/CHANGES.txt b/CHANGES.txt
index 7aa9ca1..7ea89aa 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -2,7 +2,7 @@
 =====================
 
 
-Release 0.8.0: Unreleased
+Release 0.8.0-alpha: 2015-08-29
 
 INCOMPATIBLE CHANGES
   TEZ-2048. Remove VertexManagerPluginContext.getTaskContainer()