Add installation instruction file;

Order directories.

rivista/xml/xslt.py

@@ -0,0 +1,22 @@
+#!/usr/bin/python
+# -*- coding: utf-8 -*-
+
+import xml.etree.ElementTree as ET
+
+class XmlXslt:
+
+    """This is a patch function to append XSLT reference to XML."""
+    """Why is there no built-in function of ElementTree or LXML?"""
+    def append_stylesheet(xml_data, type):
+        # Register namespace in order to avoide ns0:
+        if type == 'atom': ET.register_namespace('', 'http://www.w3.org/2005/Atom')
+        # Load XML from string
+        tree = ET.fromstring(xml_data)
+        # The following direction removes the XML declaration
+        xml_data_without_a_declaration = ET.tostring(tree, encoding='unicode')
+        # Add XML declaration and stylesheet
+        xml_data_declaration = (
+            '<?xml version="1.0" encoding="utf-8"?>'
+            '<?xml-stylesheet type="text/xsl" href="xsl/{}.xsl"?>'.format(type) +
+            xml_data_without_a_declaration)
+        return xml_data_declaration