BLD: would be helpful to have a dev version number #511
Description
e.g. current master is fixed at 2.6.1 (hard coded). maybe use https://github.com/warner/python-versioneer
IOW I was to have in tests LooseVersion(dateutil.__version__) > '2.6.1' but this is False (both on master and the released version), should be True on master.