Pycutest

This bugfix release contains the following changes:

- Migrate from setup.py to pyproject.toml (77)

There are no changes to any interface functions.

This bugfix release contains the following changes:

- Add setuptools requirement to setup.py

There are no changes to any interface functions.

Our new major release contains the following enhancements:

- New [grad() function](https://jfowkes.github.io/pycutest/_build/html/methods/pycutest.CUTEstProblem.grad.html) to evaluate the gradient only
- New [lag() function](https://jfowkes.github.io/pycutest/_build/html/methods/pycutest.CUTEstProblem.lag.html) to evaluate the Lagrangian

**Important: in order to use the new functions please clear out your cache by deleting the $PYCUTEST_CACHE/pycutest_cache_holder directory or they will not be found.**

This bugfix release contains the following changes:

- Fix invalid sparse dimensions while dropping fixed variables
- Rename equality to fixed constraints for clarity
- Restore current working directory on failure
- Fix conversion of 1x1 NumPy arrays to scalars

Note that there are no changes to any interface functions except for the renaming of the 'equality' constraints type to 'fixed' in [find_problems()](https://jfowkes.github.io/pycutest/_build/html/functions/pycutest.find_problems.html) and [problem_properties()](https://jfowkes.github.io/pycutest/_build/html/functions/pycutest.problem_properties.html) to correctly reflect that it refers to fixed variable constraints.

Our new major release contains the following changes:

- Fix memory leak in C interface (cache-breaking change)
- Modernise C interface (cache-breaking change)
- Drop Python 2.7 support as it is EOL
- Fix installs on non-default homebrew paths
- Use homebrew prefix for fallback paths on macOS
- Switch to semantic versioning

**Important: this release breaks existing cached problems, when upgrading to v1.5.0 please clear out your cache by deleting the $PYCUTEST_CACHE/pycutest_cache_holder directory.**

This release contains the following changes:

- Add guidelines for seeking support
- Improve documentation

There are no changes to any interface functions from version 1.3.