Division/multiplication between two dimensionless UnitScalars converts units type to int

When dividing between two dimensionless UnitScalars, `units` is converted to an `int`. Is this the expected behavior?

Example:

```
>>> foo = UnitScalar(1000, units='mole')
>>> bar = UnitScalar(10, units='mole')
>>> baz = foo / bar
>>> print baz.units
1
>>> print type(baz.units)

>>> foo_2 = UnitScalar(1000, units='none')
>>> bar_2 = UnitScalar(10, units='none')
>>> baz_2 = foo_2 / bar_2
>>> print baz_2.units
1
>>> print type(baz_2.units)

```