added notebooks/Persistence barcode measure to eliminate autodoc warning

Author: Francis Motta

docs/index.rst

@@ -44,7 +44,8 @@ To contribute please fork the project make your changes and submit a pull reques
     :caption: Tutorials
 
     notebooks/Classification with persistence images
-
+    notebooks/Persistence barcode measure
+    
 
 .. |Downloads| image:: https://pypip.in/download/persim/badge.svg
     :target: https://pypi.python.org/pypi/persim/