Docs have two sets of equivalent notebooks

[kandersolar]

Originally posted in https://github.com/SunPower/pvfactors/issues/136:

It seems like there are two sets of equivalent notebooks:

• https://github.com/SunPower/pvfactors/tree/master/docs/tutorials
• https://github.com/SunPower/pvfactors/tree/master/docs/sphinx/tutorials

On first glance it seems like the notebook contents are identical, with the exception of pvfactors_demo.ipynb which is only in docs/tutorials. What's the motivation to have two sets of notebooks?