Bump pyarrow from 1.0.0 to 1.0.1

See merge request !88

Perf improvements

See merge request !82

  - remove git artifacts
  - revert changes done for performance tests, that slipped into a commit

# Conflicts:
#   saqc/core/register.py
#   saqc/funcs/functions.py
#   saqc/funcs/soil_moisture_tests.py

Bump black from 19.10b0 to 20.8b1

See merge request !89

behaviour regarding type conversions, so we had to reduce our
reliance on implicit assumptions

Bump matplotlib from 3.3.0 to 3.3.1

See merge request !81

Bumps [black](https://github.com/psf/black) from 19.10b0 to 20.8b1.
- [Release notes](https://github.com/psf/black/releases)
- [Changelog](https://github.com/psf/black/blob/master/CHANGES.md)
- [Commits](https://github.com/psf/black/commits)

Sphinx

Closes #96

See merge request !84

doc-string doc of test functionality

See merge request !78

a DataFrame columns that does not exists thorws an error