Improve Gentoo support

Actually my favourite package manager is [paludis](http://paludis.exherbo.org/), so here is a support for it.
Nowadays it have only Python2 bindings, but Python3 support is [coming soon](http://paludis.exherbo.org/trac/ticket/1297)  ;) -- nowadays it works for me, but [here](https://github.com/zaufi/zaufi-overlay/tree/master/sys-apps/paludis) is a fixed ebuild for paludis w/ Python3 (waiting for gentoo team [here](https://bugs.gentoo.org/show_bug.cgi?id=493906))