Radontea

- maintenance release

- ci: skip tests that fail on GitHub Actions (Linux/macOS)

- maintenance release

- ref: cleanup

- fix: handle more special cases when computing weights for
projections (7)
- ref: make `util` submodule available upon import

- build: setup.py test is deprecated
- build: moved from travisCI to GitHub Actions
- docs: refurbish docs
- tests: allow 2D Fourier mapping test to fail on macOS
and Windows (don't know why it fails, probably unstable)
- ref: replace np.complex256 with np.complex128 in
_alg_int.py:integrate which does not break any tests but
works on Windows which sometimes has not support for longdouble
- ref: replace np.bool with bool due to numpy deprecation warnings