A wrapper to combine the uncertainties package with astropy units.
BEWARE: there is still a problem with correlations, i.e., x - x**2 returns different errors than x * (1-x)
Requires:
astropy
uncertainties
A class for handling either a value and error pair or an array pair
Usage:
>>> from astrouncertainties import *
>>> x = AUVariable([1,2,3],[1,1,1],"m")
>>> y = AUVariable([0.005,0.005,0.007],[0.001,0.001,0.001],units.km)
>>> z = x+y
>>> print z
[6.0+/-1.4142135623730951 7.0+/-1.4142135623730951 10.0+/-1.4142135623730951]*m