adding visual play button

examples/notebooks/Part 1 - Running Code.ipynb

@@ -34,7 +34,7 b''
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "Run a code cell using `Shift-Enter` or pressing the \"Play\" button in the toolbar above:"
+      "Run a code cell using `Shift-Enter` or pressing the <button class='btn'><i class=\"icon-play\" /></button> button in the toolbar above:"
      ]
     },
     {