code: function(reducer, initialValue)
    {
      for (var i = 0; i < this.length; i++)
      {
        initialValue = reducer( initialValue, this[ i ] );
      }
  
      return initialValue;
    }
docs: Reduces all the elements of this collection to a single value. All elements
  are passed to a function which accepts the currently reduced value and the
  current element and returns the new reduced value.
  
  ```javascript
  var reduceIt = function(curr, elem) {
  return curr + ( elem[0] * elem[1] );
  };
  var c = Rekord.collect([[2, 1], [3, 2], [5, 6]]);
  c.reduce( reduceIt, 0 ); // 38
  ```
  
  @method
  @memberof Rekord.Collection#
  @param {Function} reducer -
  A function which accepts the current reduced value and an element and
  returns the new reduced value.
  @param {Any} [initialValue] -
  The first value to pass to the reducer function.
  @return {Any} -
  The reduced value.