display summary in landing page

Author: jeffjennings

index-models.ipynb

@@ -7,6 +7,7 @@
    "source": [
     "# Tutorial Series on astropy.modeling\n",
     "\n",
+    "## Summary\n",
     "This is a set of tutorials on how to use the `astropy.modeling` package to model astronomical data. We will become familiar with the models available in [astropy.modeling](http://docs.astropy.org/en/stable/modeling/), learn how to make a quick fit to some data, and how to define a new model using a [compound model](http://docs.astropy.org/en/stable/modeling/#compound-models) and a custom model.\n"
    ]
   }