Surfa

- Added surface distance metrics
- Added signed distance transform utilities for image data
- Support wavefront obj file IO

- Replaced embree based ray tracing with a pure python implementation
- Improved label map utilities
- Fixed intersection, overlay, and orientation bugs

- Set numpy as automatic build dependency

- Fixed an installation bug caused by missing headers in sdist

- Added mesh transforming and fast self-intersection detection and removal
- Improved management of image geometry and transformations
- Account for image shear when saving to MGZ style file types
- NIFTI IO accounts for xyzt units and does not modify pixdim values
- Fixed bugs in freeview wrapping, spherical interpolation, and dice score

- Fixed resampling error introduced by numpy deprecations