Travis fails running tests

[tfarago]

So far I found out that this doesn't work with pint 0.5.2 and numpy 1.9.0:

from concert.quantities import q
import numpy as np
a = np.linspace(0 * q.rad, 2 * q.rad, 100)

[tfarago]

Oh man, this is just getting annoying, it is the same thing as with the built-in sum and Timer coroutine some time ago. Maybe we should stop assuming anything about pint + other (also standard) libraries because it just brakes over and over again, like here if minimum is a quantity.
I wanted to change the Range anyway, so I will take care of this with the PR for new Range (hopefully).

[tfarago]

Fixed in #336