title: Plotting two distributions in seaborn.jointplot
body: <p>I have two <code>pandas</code> dataframes I would like to plot in the same seaborn <a href="http://stanford.edu/~mwaskom/software/seaborn/generated/seaborn.jointplot.html" rel="noreferrer">jointplot</a>. It looks something like this (commands are don in an IPython shell; <code>ipython --pylab</code>):</p>
  
  <pre><code>import pandas as pd
  import seaborn as sns
  iris = sns.load_dataset('iris')
  df = pd.read_csv('my_dataset.csv')
  g = sns.jointplot('sepal_length', 'sepal_width', iris)
  </code></pre>
  
  <p>The keys in the two dataframes are identical.<br>
  How do I plot my values in the same plot (different color of course)? And even more detailed: How do I plot both dataset, but only having the distribution of the first on at the top and side? I.e. only plot the dots.</p>