add  method, alias of last_modified_at
Checking in changes prior to tagging of version 0.03.

Changelog diff is:

diff --git a/Changes b/Changes
index 5811c83..415eb93 100644
--- a/Changes
+++ b/Changes
@@ -2,6 +2,9 @@ Revision history for Perl extension Git::Repository::FileHistory

 {{$NEXT}}

+0.03 2013-07-26T11:06:29Z
+        - add `updated_at` method (alias of `last_modified_at`)
+
 0.02 2013-07-26T09:18:12Z
         - fix test cases and dependencies