title: Add column skipping nan
body: <p>I have a Series with NaNs and an array with the same length excluding NaNs values:</p>
  <pre><code>s = pd.Series([8, np.NaN, 5, 6, np.NaN, 3])
  a = np.ndarray([2, 1, 0, 4])
  </code></pre>
  <p>I want to obtain a Dataframe adding to the Series a column with the array values skipping the NaNs present on the series:</p>
  <pre><code>res = pd.DataFrame({'s': [8, np.NaN, 5, 6, np.NaN, 3],
                     'a': [2, np.NaN, 1, 0, np.NaN, 4]})
  </code></pre>
  <p>Thanks in advance for your support.</p>