Fix bug with enter in RichText.

The character (\n) is not escaped correctly, which causes that the line
break does not appear in any office version.
(Open office, Libre office or Microsoft office)

docxtpl/__init__.py

@@ -172,7 +172,7 @@ class RichText(object):
 
         if not isinstance(text, six.text_type):
             text = text.decode('utf-8',errors='ignore')
-        text = escape(text).replace('\n','<w:br/>').replace('\a','</w:t></w:r></w:p><w:p><w:r><w:t xml:space="preserve">')
+        text = escape(text).replace('\n','</w:t><w:br/><w:t>').replace('\a','</w:t></w:r></w:p><w:p><w:r><w:t xml:space="preserve">')
 
         prop = u''