Pytest-cases

* Light refactoring: some internal function names are now private, and there are now two submodules.
* [pytest-steps](https://smarie.github.io/python-pytest-steps/) is now an independent project. Examples in the documentation have been updated
* New documentation page: API reference

0.8.0 - Filtering can now be done using a callable.

* `cases_data`: the `filter` argument now contains a filtering function. WARNING: the previous behaviour is still available but has been renamed `has_tag`. Fixes [8](https://github.com/smarie/python-pytest-cases/issues/8).

* `cases_data` has a new parameters `cases` that can be used to hardcode a case or a list of cases. Its `module` parameter can also now take a list of modules

* `get_for` is deprecated: it was too specific to a given case data format.
* `MultipleStepsCaseData` was fixed to also support multiple inputs.
* Case functions can now have parameters (even case generators). This is particularly useful for test suites. Fixes [9](https://github.com/smarie/python-pytest-cases/issues/9).

* test functions can now be decorated with `test_steps` to easily define a test suite with several steps. This fixes [7](https://github.com/smarie/python-pytest-cases/issues/7).

* cases can now be decorated with `lru_cache`. `cases_generator` also provides a `lru_cache` parameter to enable caching. Fixes [6](https://github.com/smarie/python-pytest-cases/issues/6).

* New decorator `cases_generator` to define case generators. Fixes [1](https://github.com/smarie/python-pytest-cases/issues/1).
* Also, removed unused functions `is_expected_error_instance` and `assert_exception_equal`