Polliwog

Bug fixes

- Fix issue where `flipped()` creates non-contiguous arrays.

New features

- Add `polliwog.segment.path_centroid()`.

New features

- Add `polliwog.tri.surface_area()` and `polliwog.tri.sample()`.

New features

- `polliwog.plane.slice_triangles_by_plane()`: Optionally return mapping of new
faces to old.

BREAKING CHANGES

- Functions which accept triangle face indices require the dtype to be
`np.int64`.

While this restriction may be a little inconvenient for the caller, it improves
interoperability and performance, simplifies the implementation, and produces
more predictable return values. It's recommended that consuming applications
store all face indices using this dtype.

New features

- `polliwog.plane.slice_triangles_by_plane()`: Add support for slicing a
submesh.