Fix link and id of the feed

The hosts of link and id of the feed were "0.0.0.0".
I replaced {{ site.host }}, which returns 0.0.0.0, with {{ site.url }},
which returns "http://rubini.us" as defined in _config.yml.
Merge pull request #23 from vzvu3k6k/fix/feed

Fix link and id of the feed