title: resampling pandas series with numeric index
body: <p>suppose I have a pandas.Series with index with numeric value type e.g. </p>
  
  <pre><code>pd.Series( [10,20], [1.1, 2.3] )
  </code></pre>
  
  <p>How do we resample above series with 0.1 interval? look like the .resample func only work on datetime interval? </p>