add rollup method

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#	modified:   META.json
#	modified:   lib/Data/Nest.pm
#	modified:   t/01_nest.t
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Checking in changes prior to tagging of version 0.02.

Changelog diff is:

diff --git a/Changes b/Changes
index 322396e..bd52226 100644
--- a/Changes
+++ b/Changes
@@ -2,6 +2,12 @@ Revision history for Perl extension Data-Nest

 {{$NEXT}}

+0.02 2013-09-09T07:00:17Z
+
+0.02 2013-09-09T07:53:48Z
+
+    - add rollup
+
 0.01 2013-09-09T05:53:48Z

     - original version