OCaml implementation

Here's my OCaml implementation. Highlights:

* [Using a circular linked list to repeat the key](https://github.com/vigetlabs/otp/compare/dce-ocaml?expand=1#diff-dde387623ee8035f00b9d41ebd336d33R20)
* [This partial function application + map stuff](https://github.com/vigetlabs/otp/compare/dce-ocaml?expand=1#diff-dde387623ee8035f00b9d41ebd336d33R7)