Update colors() for matplotlib 2.0
matplotlib was issuing a `MatplotlibDeprecationWarning` for the use of
`rcParams['axes.color_cycle']`.  This uses the Cycler object to accomplish the same task.
@@ -719,7 +719,7 @@ def plot_vector(a, off=0+0j, *args, **kwargs):
def colors():
- return rcParams['axes.color_cycle']
+ return [c['color'] for c in rcParams['axes.prop_cycle']]
PRIMARY_PROPERTIES = network.PRIMARY_PROPERTIES
