Try to resolve relative link

Feeds might have relative links, so resolve those links according to the feed's
link.

This changeset seems to be solving issue #41. Issue #53 is still not completely
solved since the parsed feed's link is incorrect. Might want to check the atom
parser.

Signed-off-by: Fajran Iman Rusadi <fajran@gmail.com>
Merge pull request #94 from fajran/resolve-link

Try to resolve relative link