**Major changes:**
- Remove numba dependency, switch over to using Annoy nearest neighbor search. Pynndescent is now optional and can be used if installed manually.
- Massively speed-up transform by keeping reference interpolation grid fixed. Limit new points to circle centered around reference embedding.
- Implement variable degrees of freedom.
**Minor changes:**
- Add spectral initialization using diffusion maps.
- Replace cumbersome `ErrorLogger` callback with the `verbose` flag.
- Change the default number of iterations to 750.
- Add `learning_rate="auto"` option.
- Remove the `min_grad_norm` parameter.
**Bugfixes:**
- Fix case where KL divergence was sometimes reported as NaN.