add a memory leak test

[1fish2]

... based on wcEcoli/wholecell/tests/utils/test_memory_debug.py.

[prismofeverything]

I checked out the test in WCM and found it a little heavy to add, hopefully this is sufficient (it catches the issues we had before): https://github.com/CovertLab/arrow/blob/master/arrow/test/test_arrow.py#L179-L205

[1fish2]

test_memory is useful but it fails when run by itself and sometimes when run within test_arrow.

It's trying to catch native malloc leaks using psutil.Process(os.getpid()).memory_info().rss. RSS measures OS-level non-swapped physical memory allocated in whole pages. Is there a better measure of used objects on the heap?