Pytest-cases

* Major improvement of `pytest_fixture_plus`: instead of generating fixtures, it now correctly parametrizes the fixture. Skip/fail Marks are correctly copied too. Fixes [28](https://github.com/smarie/python-pytest-cases/issues/28).

* `pytest_fixture_plus` does not accept the `params` and `ids` arguments any more, it only relies on parametrization marks.

Fixed minor bug with parametrized `pytest_fixture_plus`: spaces are now correctly removed when multiple parameter names are provided in the same `parametrize` call. Fixes [27](https://github.com/smarie/python-pytest-cases/issues/27).

Fixed bug with `pytest_fixture_plus` when used in parametrized mode. Fixes [26](https://github.com/smarie/python-pytest-cases/issues/26). Thanks [Sup3rGeo](https://github.com/Sup3rGeo)!

Now using `decopatch` to create the decorators.

Cases generators can now support explicit name lists, and name generator callables, in addition to the name template strings. Fixed [24](https://github.com/smarie/python-pytest-cases/issues/24).

Dependency to `decorator` has been dropped and replaced with `makefun`. Fixed [25](https://github.com/smarie/python-pytest-cases/issues/25).

Marks on cases are now also working with pytest 3.3. Fixed [23](https://github.com/smarie/python-pytest-cases/issues/23).

Ids for marked tests are now better managed. A new function `get_pytest_parametrize_args` is now used to transform the list of cases obtained by `get_all_cases(module)`, into the list of marked cases and ids required by `pytest.mark.parametrize`. The doc has been updated to explain this for advanced users wishing to perform this step manually.