Fix issue reported in #30.

Contents of <li> elements most be wrapped inside a container like <p>.
This container is not automatically created by markdown2 unless the
list items are explicitly separated with double linebreaks.

The above issue was generating documents with invisible list items in
LibreOffice.

secretary.py

@@ -720,6 +720,17 @@ class Renderer(object):
                 # Transfer child nodes
                 if html_node.hasChildNodes():
                     for child_node in html_node.childNodes:
+                        # We can't directly insert text into a text:list-item
+                        # element. The content of the item most be wrapped inside
+                        # a container like text:p. When there's not a double linebreak
+                        # separating list elements, markdown2 creates <li> elements without
+                        # wraping their contents inside a container. Here we automatically
+                        # create the container if one was not created by markdown2.
+                        if (tag == 'li' and (not child_node.localName)):
+                            container = xml_object.createElement('text:p')
+                            container.appendChild(child_node.cloneNode(True))
+                            child_node = container
+
                         odt_node.appendChild(child_node.cloneNode(True))
 
                 # Add style-attributes defined in transform_map