v2.2.1

TL;DR: Bug fixes and optimizations.

[Features]

• SimplexTreeMulti are now pickle-able (thanks @hschreiber).
• Backend synced with gudhi PR
• Improved representation strings of slicer/simplextrees

[Fixes]

• In some situations, reading scc files from mpfree or function_delaunay was not giving the good degree
• Removed an optimization of GudhiCohomology to allow for arbitrary module presentation (@hschreiber)
• Fixed bugs preventing enabling the inf-optimization in all (non-vineyard) cases for Matrix and GudhiCohomology backends (@hschreiber).

[Optimizations]

• !Unsafe simplextree conversions are now safer, and enabled by default. This requires gudhi>=3.8.
  This can yield a significant performance (>20x) boost when converting gudhi simplextree to multipers.
• Re-enabled the inf-optimization for persistence slices with non-appearing simplices (@hschreiber).

[Documentation]

• !Changed the host to GitHub to auto-build the website with a GitHub action.