Coloraide

- **NEW**: Make `mix` use the same space logic as `interpolate` and `step`. Colors are mixed in CIELAB unless `space` is set to a different color space.
- **NEW**: Add support for blend modes as specified in [Compositing and Blending Level 1][compositing-level-1].
- **NEW**: Rename `overlay` to `compose` as all compositing (including blend modes) is done through `compose` now.`overlay` is still present and is deprecated and will be removed at some future point before a stable release. `compose` will assume `sRGB` space unless a different space is specified, but `overlay` will function as it always did.
- **FIX**: Fix some small internal issues with `in_place` logic.

- **NEW**: The adjust parameter on `interpolate`, `steps`, and `mix` has been dropped. Instead, a general purpose method
has been added to the `Color` object to mask one or more channels at a time. This can be used to create a temporary
color with masked channels for the purpose of interpolation.
- **FIX**: Ensure that when `alpha` is `NaN` that it is handled in `overlay`.
- **FIX**: When using raw data in the `color()` function, and there is too little data, fill data with `NaN`.
- **FIX**: Fix issue where API `interpolate` method does not pass `out_space` parameter down.
- **FIX**: Disabling or forcing alpha did not work properly for HSL colors via `to_string`.
- **FIX**: `contrast` and `luminance` should use XYZ with a D65 white point, not the default XYZ space which uses a D50
white point.
- **FIX**: Fix bug in Delta E 2000 algorithm.

- **NEW**: sRGB string output parameter `hex_upper` has been renamed to just `upper`. Expose it in documentation as well.

- **FIX**: More efficient calculation of CIELAB, following CIE 15.3:2004. Results are still the same, but it makes the math a little simpler.
- **FIX**: HSV did not always set hue to `NaN` when saturation was `0`.
- **FIX**: Give better conversion results by having HWB colors pass through HSV instead of sRGB.
- **FIX**: Fix slight issue with REC.2020 and ProPhoto color space conversion. Small issue when using `<=` when `<` was desired.

- **FIX**: More stable saturation calculation for HSL to ensure divide by zero doesn't occur. `2(V - L) / (1 - abs(2 * L - 1))` is likely to yield zero in the denominator when `L` is very small, while the equivalent `(V - L) / min(L, 1 - L)` is not.

- **FIX**: Ensure that when `hex`, `compress`, and `names` is enabled in `to_string` for `srgb` that colors will still match the color name if the color can be compressed.