use language names instead of flags

Per [discussion on twitter](https://twitter.com/MasseGuillaume/status/389967991279845376) flags are out, endonyms are in.

Since I won't be able to predict all combinations of sublanguages, I added a mechanism to lookup language names if it's not in the default map I provided.

> ### Language Labels
>
> Contents are assumed to be a translation when the relative path is the same. When they are detected,
> the language links appears at the bottom of each page to link to all translations.
>
> Pamflet is able to resolve some of the language codes, but you can
> provide custom language labels using `lang-` properties if it doesn't or
> just to change it:
>
>     lang-pt-BR=Português (Brasil)

Here's tetrix http://eed3si9n.com/tetrix-in-scala/.