Added deprecation warning to update_modified

Author: Denperidge

README.md

@@ -158,7 +158,7 @@ def update(the_query)
 def update_modified(subject, modified=datetime.datetime.now())
 ```
 
-> Executes a SPARQL query to update the modification date of the given subject URI (string).
+> (DEPRECATED) Executes a SPARQL query to update the modification date of the given subject URI (string).
 > The default date is now.
 
 <a id="escape_helpers.sparql_escape_string"></a>

helpers.py

@@ -144,7 +144,7 @@ def update(the_query):
 
 
 def update_modified(subject, modified=datetime.datetime.now()):
-    """Executes a SPARQL query to update the modification date of the given subject URI (string).
+    """(DEPRECATED) Executes a SPARQL query to update the modification date of the given subject URI (string).
      The default date is now."""
     query = " WITH <%s> " % MU_APPLICATION_GRAPH
     query += " DELETE {"