use 'test_harness' for parallel testing.
Added --tarball-dir option
Checking in changes prior to tagging of version 0.20.

Changelog diff is:

diff --git a/Changes b/Changes
index 97f3093..dde1ff5 100644
--- a/Changes
+++ b/Changes
@@ -2,6 +2,13 @@ Revision history for Perl extension App::perlbuild

 {{$NEXT}}

+0.20 2013-05-17T00:46:48Z
+
+    - use 'test_harness' for parallel testing.
+      (tokuhirom)
+    - Added --tarball-dir option
+      (tokuhirom)
+
 0.19 2013-05-16T02:17:08Z

     - no feature changes