svmbir v0.3.1
Changes include:
- Added support for Python 3.7; still supports Python 3.8-3.10
- Stop pinning to specific numpy (now supports numpy>=1.21)
- Update C code to normalize SV priority keys by effective SVDEPTH
- Update C code to limit threads on small problem size
- Minor clean up; allow interslice regularization =0.0
- Updated documentation for added fan beam geometry (curved, flat)