Update PyMC3_sampler_code_example.py

PyMC3_sampler_code_example.py

-import pymc3 as pm  # fork of pymc-devs/pymc master from https://github.com/aflaxman/pymc
+import pymc3 as pm 
 import numpy as np
 import matplotlib.pyplot as plt
 from pymc3.step_methods.metropolis import BinaryMetropolis