atom | rss feed generation

[just1602]

Like suggested in this issue on the leap_se repository, it would be nice to have rss | atom feeds. I really like how easy it is to manage internationalization with amber, but syndication feeds are, in my opinion, more than nice-to-have features. :)

I opened a new issue because I think it's more a generator feature than a single site feature. If I have some time I'll try to implement it myself, but I'm not really experimented in ruby and I don't have a lot of time, so if someone has some free time (lol) and can implement it, it would be nice. :P