Switch to lyon for 2D geometry tesselation

[mitchmindtree]

This is the actionable issue follow-up to #253. I'll update this comment with new steps as I work out the seemingly best way to approach it.

It's not yet clear to me whether or not we should remove nannou's 2D geom modules entirely in favour of lyon. While lyon is far better for tesselation, some of nannou's 2D geom types like Rect, Point, Range etc provide a whole suite of useful methods for easy integration with the rest of nannou's API and to be a little friendlier to new users.

For this reason, it might make sense to first replace the tesselation (triangulation) implementations first.

• lyon Point and nannou Point interop conversions.
• Create a simplified, nannou-friendly abstraction around lyon::path.
• Add implementation of GeometryBuilder for building a nannou mesh.
• Consider API options for providing fill and stroke options that makes the most of mesh and path but also allows specifying positioning, orienting, etc methods for basic shapes. Worth considering the draw "context" idea mentioned in Allow easier translation/rotation of groups of primitives #194. Going to save this for a future PR.
• Consider replacing IntoDrawn with GeometryBuilder-like API. This might address current issue with incorrect index ranges when drawing primitives that use the intermediary mesh (meshs, paths). Saving for a future PR.
• Add draw.path() API wrapping lyon path with curve support, etc.
• Replace draw primitive tesselation with lyon tesselation:
  • polyline (replaced with draw.path()).
  • polygon (working with single colour, coloured vertices blocked by Fill tessellation and keeping track of vertex colour attributes for post-tessellation interpolation nical/lyon#488).
  • ellipse
  • line
  • quad
  • rect
  • tri