Lace

- Update for Python 3.

- Fix `Mesh.intesect_plane()` method not returning a list.

- Tweak interface of `Mesh.intesect_plane()` method: don't return a list
when a neighborhood is specified.
- In collada export, make the lines red

- Add `Mesh.intesect_plane()` method from blmath
- Add utility functions for checking mesh integrity
- Migrate geometry utilities from blmath to [polliwog][]
- Migrate vector_shorcuts to [vg][]

[polliwog]: https://github.com/lace/polliwog
[vg]: https://github.com/lace/vg

- Use the new `vector_shortcuts` package.

As of this release, break from the upstream revision history and adopt ordinary
semver.

Features:

- Add `has_same_topology()` helper.
- Add `face_indices_to_flip` parameter to `flip_faces()`
- `quads_to_tris` optionally returns a mapping of old quads to new tris.
- Add new method `reorient_faces_using_normals()`

Improvements:

- Replace for loops in `flip_faces()` with vectorized operations
- Re-enable test for `flip_faces()`.
- Delegate shape geometry generation to `blmath`. Requires `1.2.5.post3` or
later.
- `landm` / `barycentric`: Refactor + improve readability

Note: This release does not include quad face support from `1.1.8.dev1`.