At the recent LBL Software Carpentry Workshop, it was pointed out that there'san inconsistency within our documentation for how to create new figures withsubplots.Indeed, most examples were using the old way, something like:    fig = plt.figure()    ax = plt.subplot(111) # or plt.add_subplot(111)This patch changes a whole bunch of instances like the above to:    fig, ax = plt.subplots()We should strive to have a minimal amount of constants in our code,especially unusual ones like `111`, which only make sense to Matlabrefugees.I have left unchanged examples which were using axes keywords passed tosubplot() and add_subplot(), since those end up transforming things like:    figure()    subplot(111, axisbg='w')to    plt.subplots(subplot_kw=dict(axisbg='w'))which isn't necessarily better.I also did not touch most of the user_interfaces examples, since those did notinvolve using plt, but instead explicitly imported Figure, and used the OOapproach on Figure instances.Also updated instaces where the old "import pylab as p" convention was used touse our standard "import matplotlib.pyplot as plt"I have also updated some, but not all uses of subplot(121) etc, but I'm a bitexhausted after doing all of these.