Add the scale to the __repr__ of a dimensionless unit.
Add dimensionless support to Unit.physical_type
Add `is_unity` method
Put scale at end, aka Unit('dimensionless with a scale of 1000.0')
Update docs to reflect new __repr__
Remove is_dimensionless
Add tests for is_unity
Remove reference to is_dimensionless in is_unity docstring
Latest round of renaming
Privatize dimensionless constant
Merge pull request #701 from mdboom/unit/dimensionless_repr

Dimensionless unit looks the same regardless of scale