Checking in changes prior to tagging of version 0.54.

Changelog diff is:

diff --git a/Changes b/Changes
index d1eb4a3..d65df63 100644
--- a/Changes
+++ b/Changes
@@ -1,5 +1,7 @@
 Revision history for Perl extension CGI::Header.

+0.54 (1.00-RC7) May 20th, 2013
+
   - Rename CGI::Header#as_string to "finalize" since CGI.pm's header()
     method returns an empty string in "mod_perl" environment
   - Remove CGI::Header::Standalone