Add that image from the README into the repo

Author: Hugo Osvaldo Barrera

README.rst

@@ -1,10 +1,10 @@
-.. image:: example_ean13.png
+python-barcode
+==============
+
+.. image:: example-ean13.png
   :target: https://github.com/WhyNotHugo/python-barcode
   :alt: python-barcode
 
-pyBarcode
-=========
-
 This library provides a simple way to create barcodes using only the
 Python standard lib. The barcodes are created as SVG objects.