Fix Matplotlib warning about axes.color_cycle
Fix Matplotlib warning about axes.color_cycle

Warning message:
"/Users/mesnardo/src/anaconda/envs/python2/lib/python2.7/site-packages/matplotlib/__init__.py:872:
UserWarning: axes.color_cycle is deprecated and replaced with axes.prop_cycle;
please use the latter."

Replace with `axes.prop_cycle`; no more warning.

mesnardo/PetIBM,mesnardo/PetIBM,mesnardo/PetIBM,piyueh/PetIBM,barbagroup/PetIBM