[CM] musx 3.0.0 release

[Taube, Rick]

Hi folks, just an FYI that I have released a major new version of the musx package on the pypi website https://pypi.org/project/musx/

Here are the highlights:

* The musx demo scripts have been converted from .py files into Jupiter Notebooks (.ipynb) to better facilitate interactive exploration. 
* A new tutorials directory contains a number of Jupyter Notebooks adapted from my CS+Music classes at UIUC. The topics are wide ranging, from basic data representation to spectral composition and 'real time' extensions.
* Support for loading data from MusicXML files into data structures that can be easily mapped for analysis.  The MusicXML support is located in the musx.mxml module and contains notation classes (enumerations), parts and scores.
* A new pattern.py module provides a base Pattern class that support for sub-patterns (patterns inside patterns), a new Range pattern, a new Graph pattern, "dynamic values" (values that can be constants or lambda expressions of zero arguments), and dynamic weighting in the Choose pattern. The new patterns.py module replaces the older gens.py module, which can be still loaded using the explicit command 'import musx.gens'.
* New module frac.py adds methods to Python's Fraction class for working with tuples and other mensural quantities.

You can access the code, documentation, demos, and tutorials on the musx github website:

    https://github.com/musx-admin/musx

Please see the INSTALL.md file for instruction on how to set up the musx package in a hygenic virtual environment.

My next step will be to integrate Todd Ingalls' pysndlib wrapper around sndlib to generate audio files -- at that point musx will be doing pretty much everything that Grace did with some new things as well.

--Rick