update online docs to include binder links

docs/examples/index.rst

@@ -4,7 +4,13 @@ Examples
 We have several examples to illustrate various features of the code. These
 notebooks have been rendered here for the web, but the originals are
 found in the ``examples/`` directory of the package, and you can run them
-yourself!
+yourself! 
+
+You can also try them out online directly from your browser: 
+.. image:: https://mybinder.org/badge_logo.svg
+ :target: https://mybinder.org/v2/gh/dwhswenson/contact_map/master?filepath=%2Fexamples
+
+(Note: the performance of the online servers can vary widely.)
 
 .. toctree::
     :maxdepth: 1