Change examples/tutorials to jupyter notebooks

[larsbratholm]

The current ones are in markdown. It would probably be better to change these to notebooks so people can edit them and that they are automatically updated with code changes.

[larsbratholm]

An alternative to this is to do something similar to https://dask-ml.readthedocs.io/en/latest/
Markdown can apparently run ipython on pieces of code. and we can include a binder link to a separate notebook. I'm not sure what the best approach is.
Also #54 #56 .