Add allow_pureperl option to Module::Build
Checking in changes prior to tagging of version 0.21.

Changelog diff is:

diff --git a/Changes b/Changes
index 6f77fee..c35b881 100644
--- a/Changes
+++ b/Changes
@@ -2,6 +2,9 @@ Revision history for Algorithm::HyperLogLog

 {{$NEXT}}

+0.21 2013-06-25T17:42:09Z
+    - Fixed '--pureperl-only' option support
+
 0.20 2013-06-23T09:09:42Z
     - Change dependency
     - Switch aurhoring tool to Minilla