Files not cleaned up during unit tests for "evaluation" components

[browningjp-datatonic]

The following files are created during the unit tests of the "evaluation" components, but are not cleaned up

• pipeline_components/evaluation/example_count.py
• pipeline_components/evaluation/plots_num_feat.html
• pipeline_components/evaluation/plots_overall.html

These files should be cleaned up automatically during the unit tests (ideally using a tmpdir fixture or similar - they need to be cleaned up regardless of whether the tests pass)