#206 Fix XHTML namespace normalisation for missing scheme

[Anthony Pessy]

The following cleanup in HtmlCleaner:

                    if (ns.equals("https://www.w3.org/1999/xhtml") || ns.equals("http://w3.org/1999/xhtml")){
                        ns = "http://www.w3.org/1999/xhtml";
                        Map<String, String> attributes = startTagToken.getAttributes();
                        attributes.put("xmlns", "http://www.w3.org/1999/xhtml");
                        startTagToken.setAttributes(attributes);
                    }

Should be replaced by:

                    if (ns.endsWith("//www.w3.org/1999/xhtml") || ns.endsWith("//w3.org/1999/xhtml")){
                        ns = "http://www.w3.org/1999/xhtml";
                        Map<String, String> attributes = startTagToken.getAttributes();
                        attributes.put("xmlns", ns);
                        startTagToken.setAttributes(attributes);
                    }

In order to:

• handles case where scheme is not specified
• DRY cleaned namespace name