added new module: Web::Query::LibXML

Modified test files to also test Web::Query::LibXML if it loads.
Checking in changes prior to tagging of version 0.22.

Changelog diff is:

diff --git a/Changes b/Changes
index 7863232..ba093d2 100644
--- a/Changes
+++ b/Changes
@@ -2,6 +2,11 @@ Revision history for Perl extension Web::Query

 {{$NEXT}}

+0.22 2013-05-15T23:36:38Z
+
+    - added new module: Web::Query::LibXML
+    - modified test files to also test Web::Query::LibXML (if it loads).
+
 0.21 2013-05-15T14:36:11Z

     - new jQuery-compatible method: add()