ensure people start up JupyterHub sooner than later for lec 2

Author: afeld

lecture_2_exercise.ipynb

@@ -12,6 +12,7 @@
    "source": [
     "# Lecture 2 in-class exercise\n",
     "\n",
+    "1. [Make a copy of this notebook.](https://python-public-policy.afeld.me/en/{{school_slug}}/assignments.html#getting-started)\n",
     "1. Find a dataset that seems interesting on the [NYC Open Data Portal](https://opendata.cityofnewyork.us/).\n",
     "    - Find something in a tabular format rather than a map, etc.\n",
     "    - Don't spend long on this.\n",