Fix hadoop-yarn-project/CHANGES.txt for YARN-759

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1493842 13f79535-47bb-0310-9956-ffa450edef68

hadoop-yarn-project/CHANGES.txt

@@ -126,6 +126,8 @@ Release 2.1.0-beta - UNRELEASED
     YARN-724. Moved ProtoBase from api.records to api.records.impl.pb. (Jian He
     via vinodkv)
 
+    YARN-759. Create Command enum in AllocateResponse (bikas)
+
     YARN-777. Removed unreferenced objects from .proto files. (Jian He via
     vinodkv)