Fixed CREDITS file and include it in package.xml too

Author: derickr

CREDITS

@@ -1,3 +1,2 @@
-;; phongo
-Hannes Magnusson [bjori] <bjori@mongodb.com> (lead)
-Jeremy Mikola [jmikola] <jmikola@mongodb.com> (developer)
+MongoDB Driver for PHP
+Hannes Magnusson, Jeremy Mikola, Derick Rethans

bin/prep-release.php

@@ -80,6 +80,7 @@ function get_files() {
       'doc' => array(
         "README*",
         "LICENSE",
+        "CREDITS",
       )
     );
     $files = array();