Add section for unreleased 1.0.4 to CHANGES.txt

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.0@1361046 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -1,5 +1,13 @@
 Hadoop Change Log
 
+Release 1.0.4 - Unreleased
+
+  NEW FEATURES
+
+  IMPROVEMENTS
+
+  BUG FIXES
+
 Release 1.0.3 - 2012.05.07
 
   NEW FEATURES