Add a flipping module.

I thought you may be interested in taking this module? It has been ported from Minichan/javascript/flip.js.

```
<penthief> !flip abcdefghijkmnrtvwy ABCDEFGJLMPRTUVY 12345678 ,.?!"\` ()[]{<>&_'
<jsminnie-unstable> penthief: ,‾⅋<>}[]() ,\,¡¿˙' 8ㄥ9ϛㄣƐᄅƖ ⅄Λ∩┴ɹԀW˥ſפℲƎpƆq∀ ʎʍʌʇɹuɯʞɾᴉɥƃɟǝpɔqɐ
<penthief> !flip ‾⅋<>}[]() ,\,¡¿˙' 8ㄥ9ϛㄣƐᄅƖ ⅄Λ∩┴ɹԀW˥ſפℲƎpƆq∀ ʎʍʌʇɹuɯʞɾᴉɥƃɟǝpɔqɐ
<jsminnie-unstable> penthief: aBcDefghijkmnRtvwy ABCDEFGJLMPRTUVY 12345678 ,.?!'\' ()[]{<>&_
```