Ripser

- Adding link to ripser++ GPU version by Simon Zhang

- Cocycle indices now correspond to point cloud indices, even
when a greedy permutation is in use

- Fixed packing so C++ is MSVC compatible.

- Added license to distributed packages.

- Added support for greedy permutations.
- Outsourced plotting to persim.
- Outsourced data construction in examples to tadasets.
- Revamped documentation.

- Completed JOSS review, thanks lmcinnes and arokem!!
- Documentation details updated.