adding visual interrupt 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 <button class='btn'><i class=\"icon-play\" /></button> button in the toolbar above:"
+      "Run a code cell using `Shift-Enter` or pressing the <button><i class=\"icon-play\" /></button> button in the toolbar above:"
      ]
     },
     {
@@ -79,7 +79,7 b''
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "Code is run in a separate process called the IPython Kernel.  The Kernel can be interrupted or restarted.  Try running the following cell and then hit the \"Stop\" button in the toolbar above."
+      "Code is run in a separate process called the IPython Kernel.  The Kernel can be interrupted or restarted.  Try running the following cell and then hit the <button><i class='icon-stop'/></button> button in the toolbar above."
      ]
     },
     {