Spm12

- update test framework (10)
- add py3.9

- misc framework & test updates (9)
- add pre-commit hooks
- minor build fixes

- use `miutil.mlab.get_engine` (8)
- update documentation
- update build framework
+ add auto-versioning
+ update dependencies
+ add test coverage reporting

- fix Windows installation

First Release :tada:

- `get_matlab()` automatically finds and installs `matlab.engine`
+ supports multiple environments (`conda`/`virtualenv`/home)
+ re-uses engines across different function calls
+ can specify custom engine names
- `ensure_spm()` automatically downloads and adds `SPM12` to `matlab.engine`'s path
- provide `coreg_spm()` and `resample_spm()` convenience functions; more to come!