make test fails because it can't find `pip2`
Trying it with normal pip
Changed amount of memory needed for test_save_load_merge
Reduced memory requirements for test_counting_single.py
Deleted KhmerError and all references to it.
Builds succesfully, `make test` runs without error.
Updated Changelog
Modified test_counting_single.py to pass the tests.
backed out changes to Makefile (references to pip2)
Merge pull request #542 from leonorgg/fix/444

Fix/444
Adding a description to the Changelog
Merge branch 'drlabratory-fix/503'