Checking in changes prior to tagging of version 0.23.

Changelog diff is:

diff --git a/Changes b/Changes
index fe61504..03b9831 100644
--- a/Changes
+++ b/Changes
@@ -2,6 +2,10 @@ Revision history for Algorithm::HyperLogLog

 {{$NEXT}}

+0.23 2014-05-12T16:58:51Z
+    - Add new method 'Algorithm::HyperLogLog::merge()'
+        (dgryski)
+
 0.22 2013-06-25T22:54:20Z
     - Fixed broken test