title: in dataframe , how to merge two rows
body: <p>in dataframe , how to merge two rows, like <code>148</code> merge <code>142</code> to be a new line and drop two them.</p>
  
  <pre><code>          title  collectionsCount  subscribersCount  entriesCount  viewsCount
  148     Android            697977            100213          6803    10610138
  142        Java            103821             65303          1493     1590201
  161         iOS            163137             65896          3601     3739843
  177  JavaScript            222100             88872          2412     3548736
  16       Python             45234             45100          1007      930588
  162       Swift             28498             30317          1180      928488
  20          PHP             15376             25143           375      329720
  62           Go              5321             12881           179      145851
  41          C++              3495             18404           101       75019
  17            C              2213             14870            50       52019
  63         Ruby              1543              6711            40       45162
  </code></pre>