Array.Rotate

/*
A function that rotates a 2-dimensional array by 90 degrees.

> _([ 
      [1, 2, 3], 
      [1, 2, 3], 
      [1, 2, 3] 
    ]).rotate().value()
  
    [ 
      [ 1, 1, 1 ], 
      [ 2, 2, 2 ], 
      [ 3, 3, 3 ] 
    ]

Written so generic-structure objects can be arranged in HTML tables:
    
> _([ 
      ["john", "m", 21], 
      ["Jane", "f", 34] 
    ]).rotate().value()
  
  [ 
    [ 'john', 'Jane' ], 
    [ 'm', 'f' ], 
    [ 21, 34 ] 
  ]
*/



_.mixin({rotate: function rotate (arr) {
  // get the maximum length of the sub-arrays:
  var length = arr.reduce(function (max, inner_array) { return inner_array.length > max ? inner_array.length : max }, 0)
  // Init a new array of that size and fill it.
  return _.range(length).map(function (i) {
    return arr.map(function (arr) {return arr[i]})
  })
}})