Feature Request: "rotate"

I miss a function to rotate a Matrix/Vector:
```ruby
m
# [ [ 1 2 3 ]
#   [ 4 5 6 ] ]
n = m.rotate_clockwise(1) # rotate clockwise, "one time"
n
# [ [ 4 1 ]
#   [ 5 2 ]
#   [ 6 3 ] ]
```

Excuse my rusty math brain, maybe it is already implemented but named differently, in which case the documentation might be improved to mention the word "rotate" :)
