Non recursive add simplex

[maximelucas]

• rewrite of add_simplices_from so that is is non-recursive.
• updated tests

With the rewrite, we first add all input simplices, store all faces, and add the faces add the end. It used to add each input simplex with its faces, so this changes the order in which simplices are added. This new order solves #244

Notes:

• to avoid too much redundancy and slowness, we add the set of faces. This seems to sometimes randomly change the order of simplices.
• one test does not pass: test_boundary_matrix. I think it's cause by the change in order which causes simplices to have different IDs. Might need @Marconurisso to check on this one.
• need to check if remove_simplex_ids_from does not enforce removing subfaces #85 is still a problem
• I commented out some test lines that were catching warning when adding simplices because they were making the tests infinitely slow. I had to ctrl+c my way out everytime. No idea why.

[maximelucas]

• test_boundary_matrix now passes - thanks @Marconurisso
• remove_simplex_ids_from does not enforce removing subfaces #85 is fixed
• put the warning tests back in: they were slow because of an infinite loop - now fixed
• versions 3.7 and 3.10 of python have a different "order" for sets. Added some +SKIP flags in doctests when they failed because of that.

[nwlandry]

I did a few tests of my own, adding/removing simplices, etc. and everything works flawlessly! This is great work!!