Pypardiso

- remove mkl-service dependency (fixes [24](https://github.com/haasad/PyPardisoProject/issues/24) and [#26](https://github.com/haasad/PyPardisoProject/issues/26))
- `get_max_threads` and `set_num_threads` methods are removed from the `PyPardisoSolver` class, use `mkl-service` directly if you require them
- change how the shared_library `mkl_rt` is detected to account for differences between conda and pip
- also removes the psutil dependency

This is the last release with a manual changelog. The old CHANGELOG.md file can be viewed [here](https://github.com/haasad/PyPardisoProject/blob/310bc3705c7334545dd7ed3b96cdaaf967262976/CHANGELOG.md).

* Change requirements in setup.py to fix [failing conda-forge build](https://github.com/conda-forge/staged-recipes/pull/15106#discussion_r654696146)

Revert to the old way of detecting the mkl_rt library on osx, since psutil doesn't work (see [14])

Changed how pypardiso detects the __mkl_rt__ library to fix a breaking change on windows with [mkl 2021.2.0](https://anaconda.org/conda-forge/mkl). See [#12](https://github.com/haasad/PyPardisoProject/issues/12) for details.