Add a *simple* arrow example

Author: dmcdougall

examples/pylab_examples/arrow_simple_demo.py

@@ -0,0 +1,6 @@
+import matplotlib.pyplot as plt
+
+fig = plt.figure()
+ax = fig.add_subplot(1, 1, 1)
+ax.arrow(0, 0, 0.5, 0.5, head_width=0.05, head_length=0.1, fc='k', ec='k')
+plt.show()