title: Negative numbers don't display correctly in matplotlib xkcd style
body: <p>I've been playing with the xkcd style feature in matplotlib. I have Matplotlib 1.4, and the humor sans font is installed correctly, or works in msword at least. </p>
  
  <p>When I run the following example code, I get "?" instead of "-" on labels any time there should be a negative number. Any idea what causes this?</p>
  
  <pre><code>with plt.xkcd():
    plt.figure()
    plt.plot(np.sin(np.linspace(0, 10)))
    plt.title('Whoo Hoo!!!')
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/lUp1Q.png" alt="enter image description here"></p>
  
  <p>Edit: At Bernie's suggestion (thanks Bernie) I tried some different backends. Tried Qt, Tkinter, and inline, and none seem to work. I'm using Ipython 2.3 btw.</p>
  
  <p>Also, reputation is now high enough to post an image. As you can see everything is as expected except those pesky question marks.</p>