wip/py-test-nbval 0.9.6 NetBSD

The plugin adds functionality to py.test to recognise and collect Jupyter notebooks. The intended purpose of the tests is to determine whether execution of the stored inputs match the stored outputs of the `.ipynb` file. Whilst also ensuring that the notebooks are running without errors.

The tests were designed to ensure that Jupyter notebooks (especially those for reference and documentation), are executing consistently. Each cell is taken as a test, a cell that doesn't reproduce the expected output will fail.