Holoviz

Updated pinning to latest versions of the HoloViz stack and made corresponding updates to the tutorial.

* HoloViews 1.13.2
* Datashader 0.11.0
* hvPlot 0.6.0
* param 1.9.3
* Panel 0.9.5

The 0.11.3 release (and presumably previous ones) were not pinned properly, letting them float upwards and encounter various warnings and errors as dependency APIs changed over time. This release makes minor fixes and pins to the versions in use at the time 0.11.3 was written, with minimal changes otherwise.

Initial HoloViz release, to support SciPy 2019 tutorial.

This release contains a major update to both the PyViz environment and the tutorial materials. The two main changes to the tutorial materials consisted of updating all the materials to replace the use of IPython magics with the new and now recommended HoloViews ``.opts`` API. Additionally all examples using the paramnb and parambokeh libraries have now been replaced with the new panel library which is much more capable.

The other major changes were to the dependencies which were updated to the latest versions of both the PyViz and PyData ecosystems. In particular there are major updates to HoloViews, GeoViews, hvPlot, and the addition of the newly published panel library.

Adds support for recent Panel versions. Still requires dev releases of some packages, so installation is from the pyviz dev channel.