Add a test for the race between dumping a dataset and deleting keys in it
Mark test slow via nose attrib plugin
Replace finish order requirement with a duration requirement
Add a check for 'none' key type when dumping, which can occur if a concurrent process is deleting keys
A key may be deleted between the calls to type and get
Python 3 compatibility
Check remaining key types
Only print times when running a subprocess
Document behavior under concurrent modifications
Redo dumping to handle keys changing types