v0.1.0-dev.0

This is the first pre-release version of Kludgine. This milestone represents the first time I felt like Kludgine's API reached some sort of "complete" state post-refactor. The major takeaways are:

• Removed all user interface code, and spun off a new user interface project,
  Gooey.
• Split Kludgine into three crates:
  • kludgine-core: The rendering aspects of Kludgine. Can now be used for headless rendering as well.
  • kludgine-app: The windowing/event handling layer of Kludgine.
  • kludgine: An omnibus crate that marries the two with one crate include.
• Now uses figures for its math types. If you're using functionality that was
  in euclid but is no longer available in figures, please submit an
  issue. We may not add all
  requested functionality, but as long as it extends one of the types figures
  already has, it likely will be added upon request.
• Introduced unstable-apis feature flag. The plan for this flag is to offer a
  way to provide APIs that are still under heavy development to be used without
  forcing semver updates when the APIs change. After 1.0, breaking changes to
  unstable-apis will be one of the factors that causes minor version
  increments.