Replaced the dependancy to xlsx by openxlsx, which doesn't rely on xlsxjars and rJava and is much faster !

DESCRIPTION

@@ -6,7 +6,7 @@ Date: 2013-09-18
 Author: Maxime Wack
 Maintainer: Maxime Wack <maximewack@free.fr>
 Depends:
-    xlsx
+    openxlsx
 Description: This package aims at the easy production of descriptive and
     bivariate statistics tables in HTML. It can load files in csv, xls/xlsx
     formats, and read labels and formats from SAS or plain text files. It is