code: function(diffArray) {
      for (var i=0, head=0, result=[], len=diffArray.length; i<len; i++) {
        head = head + diffArray[i];
        result.push(head);
      }
      return result;
    }
docs: Converts an array of diffs to array of values
  for example : [100, 1, 1, 1, 1, 1] => [100, 101, 102, 103, 104, 105]
  @param {array<number>}
  @return {array<number>}