Added credits.

Author: donnemartin

scikit-learn/scikit-learn-intro.ipynb

@@ -11,6 +11,8 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
+    "Credits: Forked from [PyCon 2015 Scikit-learn Tutorial](https://github.com/jakevdp/sklearn_pycon2015) by Jake VanderPlas\n",
+    "\n",
     "* Machine Learning Models Cheat Sheet\n",
     "* Estimators\n",
     "* Introduction: Iris Dataset\n",