title: Forcing exact boundaries in matplotlib's histogram
body: <p>If I feed a collection of values to matplotlib's histogram, I get a min and max boundary that has been rounded to a nice number.</p>
  
  <p>E.g. if I feed values between -1 and 18.4, my histogram axis will run from -10 to 50.</p>
  
  <p>Is there a way to force the axis to be a perfect fit for the data, without padding?</p>