Remove future session drafts, will add back to this branch as it develops
Merge branch 'staging' of github.com:UCL/rsd-engineeringcourse into staging

* 'staging' of github.com:UCL/rsd-engineeringcourse:
  Update 07debugging.md
  Update 05nose_exercise.md
  Correct spelling of arbitry
  Remove unused import of abs.
  remove .py on test names (Mid-lecture fix!)
  Fit Testing session into reveal slides