Fix/444

I reduced the memory requirements for test_counting_single.py
(Please ignore changes to test_save_load_merge, jlippy has fixed test_subset_graph.py)

Checklist:
- [ y ] Is it mergable
- [ y ] Did it pass the tests?
- [ no new functionality ] If it introduces new functionality in scripts/ is it tested?
  Check for code coverage.
- [ y ] Is it well formatted? Look at `pep8`/`pylint`, `cppcheck`, and
  `make doc` output. Use `autopep8` and `astyle -A10 --max-code-length=80`
  if needed.
- [ y ] Is it documented in the Changelog?
- [ y ] Was spellcheck run on the source code and documentation after changes
  were made?