Ppb-mutant

Mutant Standard Emoji has made their [April 2020 Release](https://blog.mutant.tech/index.php/2020/04/28/mutant-standard-april-2020/), and so ppb-mutant has been updated.

No other code changes have been made. See the release announcement above for their changelog.

(This fixes a previous v0.11.0 release that was botched.

This release is for PPB v0.8 and Mutant v2020.02.

We're now using the upstream 128px renders instead of making our own 64px ones. There will be some increase in file sizes, but not as much as you'd expect.

In addition, support has been added for the new hoof morph type.

Full changelog:

* New morph type `'hoof'` and added `TONES_HOOF`
* Emoji `color_modifier` and `hand_splayed` got some help for some missing versions
* `color_modifier` with `tone=None` is mapped to `tone='k2'` (k2 is the default color)
* `hand_splayed` with `morph='paw'` is mapped to `hand` (paws are always splayed)
* Added `SelectScene.include_hoof` because hoof coverage is incomplete (expect it to be removed in the future)
* `MorphToneProxy` now only reloads if it's an aliased shortcode (no user-visible difference)
* `ppb_mutant.index` grew a loading screen
* Build dramatically simplified

v0.9.0 left out some necessary files. This release fixes that.

This updates for PPB v0.7 and Mutant Standard Emoji v0.4.1

PPB v0.7 dramatically altered how images are loaded via its new Asset system, and ppb-mutant was rewritten to be based on it.

* `MutantSprite` is now deprecated. Just use `ppb.Sprite` with `image = Emoji(...)`
* Added `Emoji`, which is an asset that takes the shortcode, morph, and tone.
* Added `MorphToneGroup`, which is a way to change the morph and tone of a whole group of Sprites at once.

All the internals were also updated for the VFS system.

Updates to support PPB v0.6, and a collection of bugfixes. The biggest user-facing change is:

* The full category path is no longer necessary. Just the shortcode. (That is, use `'slime'` instead of `'people_animals/creatures/other/slime'`)

This release just updates the emoji set to Mutant Standard Emoji v0.4.0.