Set Jupyter Notebook to have both python2 and python3 kernels

Run:
```
conda create -n py27 python=2.7 ipykernel
conda create -n py36 python=3.6 ipykernel
```

Source: https://stackoverflow.com/questions/30492623/using-both-python-2-x-and-python-3-x-in-ipython-notebook