Update matplotlib to 3.2.0

[pyup-bot]

This PR updates matplotlib from 1.4.0 to 3.2.0.

Changelog

3.2.0rc1

This is the first release candidate from Matplotlib 3.2

3.1.1

The first bug-fix release of the 3.1 series

* Locator.nonsingular return order API change

Lots of backports of various bug fixes.

2.1.0

This is the second minor release in the Matplotlib 2.x series and the first
release with major new features since 1.5.

This release contains approximately 2 years worth of work by 275 contributors
across over 950 pull requests.  Highlights from this release include:

- support for string categorical values
- export of animations to interactive javascript widgets
- major overhaul of polar plots
- reproducible output for ps/eps, pdf, and svg backends
- performance improvements in drawing lines and images
- GUIs show a busy cursor while rendering the plot


along with many other enhancements and bug fixes.

2.0.0

Major release of Matplotlib

This release completely overhauls the default style of the plots.

Highlights include:
- 'viridis' is default color map instead of jet.
- Modernized the default color cycle.
- Many more functions respect the color cycle.
- Line dash patterns scale with linewidth.
- Change default font to DejaVu, now supports most Western
alphabets (including Greek, Cyrillic and Latin with diacritics),
math symbols and emoji out of the box.
- Faster text rendering.
- Improved auto-limits.
- Ticks out and only on the right and bottom spines by default.
- Improved auto-ticking, particularly for log scales and dates.
- Improved image support (`imshow` respects scales and eliminated a
class of artifacts).

Links

• PyPI: https://pypi.org/project/matplotlib
• Changelog: https://pyup.io/changelogs/matplotlib/
• Homepage: https://matplotlib.org

[pyup-bot]

Closing this in favor of #438