Increasing version to get latest dependencies into PyPI release

Updates to support Python 3.9, and fix bugs with plotting data with NaNs:
Updating required pyqtgraph version to 0.11.1
Updating required pyqt5 version to 5.15.2
Bumping required Python version to 3.6

Updating to get Windows bug fix into PyPI AND Anaconda

Hoping this one works

Updating to get Windows bug fix into PyPI

trying again

v1.7.10: updating version number

to get tplot_names bug fix

First Release

Releasing pytplot to get a DOI