== Array#rotate

  require 'facets/array/rotate'

clockwise

  a = [1,2,3]
  r = a.rotate
  r.assert == [2,3,1]

counter-clockwise

  a = [1,2,3]
  r = a.rotate(-1)
  r.assert == [3,1,2]

== Array#rotate!

clockwise

  a = [1,2,3]
  a.rotate!
  a.assert == [2,3,1]

counter-clockwise

  a = [1,2,3]
  a.rotate!(-1)
  a.assert == [3,1,2]

