title: interpolating consecutive numbers
body: <p>Based on below Pandas DataFrame, there are time(second) &amp; heartrate values.
  Although 'time' should be consecutive numbers, we see some missing values. (1,2,4,5,7,9,10 etc) In that case, should I use pandas.DataFrame.interpolate to get desired result? or any other great idea to achieve it? Please note the original data are coming from API. I tried to look for any answers on the web, but no luck...</p>
  <p>Original:</p>
  <pre><code>    time heartrate
      0   97
      3   105
      6   105
      8   111
      11  111
      13  114
      16  115
  </code></pre>
  <p>Desired output:</p>
  <pre><code>time    heartrate
  0   97
  1   100
  2   103
  3   105
  4   105
  5   105
  6   105
  7   109
  8   111
  9   111
  10  111
  11  111
  12  113
  13  114
  14  114
  15  114
  16  115
  </code></pre>