title: Matplotlib.plot Histogram has extra space
body: <p>I'm not sure how to word this; when I create my histogram it should have values from 0 to 255 [black to white values in shades of gray], but it almost always goes to around 300.  Is there something in my code which is messing around with the x-range?</p>
  
  <pre><code>from PIL import Image
  import matplotlib.pyplot as plt
  import urllib, cStringIO
  
  file = cStringIO.StringIO(urllib.urlopen("http://www.animal-photos.org/_photo/2715313.jpg").read())
  im = Image.open(file)
  im = im.convert("L")
  data = list(im.getdata())
  plt.hist(data, color = "gray", bins = 256, label = "Gray Histogram", )
  plt.xlabel("Gray Value (0,256)")
  plt.show()
  </code></pre>
  
  <p>The first part [the file part] has been added just so that the code actually runs; the URL was just a black-and-white jpg that I had open.  The program cuts up the image and tells us via histogram how many pixels there are of varying grayness (given by a value 0 to 255).</p>