Checking in changes prior to tagging of version 0.13.

Changelog diff is:

diff --git a/Changes b/Changes
index f0f738d..7d5a697 100644
--- a/Changes
+++ b/Changes
@@ -1,5 +1,9 @@
 Revision history for Perl extension CGI::Header::PSGI.

+0.13  Apr 22nd, 2013
+
+  - Requires CGI::Header 0.49 or higher
+
 0.12  Apr 13th, 2013

   [BUG FIX]