Moneta or Rails key store value with file

Hi,

Im trying to find a key value store mechanism on rails 3 that either
use activerecord or file store.
I found moneta but couldn't find how to use or initialize it on rails
3 environment.

any body could show how to do this ? or maybe there is something other
than moneta i could use.
I just need a uniform and fast way to access setting on my app like

Setting.post_per_page

thanks before