Enhance `u_bar` function in order to partition triangles.
Add doctests for `u_bar` function enhancement about triangles' partitions.
WIP: make iterations on upside down triangles work.
WIP: planning about indices should be finished.
WIP: write the function that barycentric combines a given triangle.
Almost finish degree elevation, some refactoring is pending.
Add a function that repeat drawing degree elevation algorithm's results.
Fix the first way to draw repeated degree elevation.
Finish a presentable version of *degree elevation* algorithm.