intro_tutorial: Warn user the Mesa version must be up-to-date

docs/tutorials/intro_tutorial.ipynb

@@ -12,6 +12,7 @@
    "metadata": {},
    "source": [
     "## Tutorial Description\n",
+    "Important: you must ensure that your Mesa version is up-to-date in order to run this tutorial.\n",
     "\n",
     "[Mesa](https://github.com/projectmesa/mesa) is a Python framework for [agent-based modeling](https://en.wikipedia.org/wiki/Agent-based_model). This tutorial will assist you in getting started. Working through the tutorial will help you discover the core features of Mesa.  Through the tutorial, you are walked through creating a starter-level model. Functionality is added progressively as the process unfolds. Should anyone find any errors, bugs, have a suggestion, or just are looking for clarification, [let us know](https://github.com/projectmesa/mesa/issues)!\n",
     "\n",