Removed white space char that breaks validation

The extra newline char between <?xml version="1.0" encoding="UTF-8"?> and the <rss> tag breaks what would otherwise be a valid feed.  It's only there for aesthetic reasons anyway so it should be removed.

lib/index.js

@@ -181,7 +181,7 @@ function RSS (options, items) {
     };
 
     this.xml = function(indent) {
-        return '<?xml version="1.0" encoding="UTF-8"?>\n' +
+        return '<?xml version="1.0" encoding="UTF-8"?>' +
             xml(generateXML(this), indent);
     };
 }