Release v2.1.0.

Release v2.0.0.

Release v1.5.1.

Pin indirect docs requirements.

Release v1.4.1.

Explicitly import some submodules to help IDE autocomplete

Release v1.3.5

Release v1.3.4

- Missing `from builtins import super` in _vtk_errors meaning that pr…

…evious

  version is broken in python2. Turns out there is a bug in pip 20 in python2
  so that `pip install -U .` doesn't work. Meaning I was testing an old
  vtkplotlib version without realising and consequently the above slipped
  past unittesting. But fixed now.
- Ditching pkg_resources as it's super slow. I've finally found the docs
  that say what it's for and it turns out it is only necessary if
  vtkplotlib is zipped. As vtkplotlib is not zipsafe anyway this isn't an
  issue.

Forgot to copy `off_screen` argument from `save_fig()` to `screenshot…

…_fig()`