title: Using pandas crosstab to create a bar plot
body: <p>I am trying to create a stacked barplot in seaborn with my dataframe.</p>
  <p>I have first generated a crosstab table in pandas like so:</p>
  <pre><code>pd.crosstab(df['Period'], df['Mark'])
  </code></pre>
  <p>which returns:</p>
  <pre><code>  Mark            False  True  
  Period BASELINE    583    132
         WEEK 12     721      0 
         WEEK 24     589    132 
         WEEK 4      721      0
  </code></pre>
  <p>I would like to use seaborn to create a stacked barplot for congruence, ans this is what I have used for the rest of my graphs. I have struggled to do this however as I am unable to index the crosstab.</p>
  <p>I have been able to make the plot I want in pandas using <code>.plot.barh(stacked=True)</code> but no luck with seaborn. Any ideas how i can do this?</p>