1.8.0 - pytest-xdist compliance

• For each of the [module/session]_results_[dct/df] fixtures, an equivalent get_<fixture_name>(session, ...) helper function is available. This allows users to access the same level of functionality than the fixture, in places where fixtures are not available (typically in a pytest hook such as the pytest_sessionfinish session finish hook). In addition the default FIXTURE_STORE is now a package variable, available directly or through the session-scoped fixture_store fixture. Fixed #33 and #34.

• Added an example in the documentation on how to use with pytest-xdist. Fixes #32

See documentation page for details.