Support multiple links

[makew0rld]

This adds a Links var to Feed and Items. This was mainly created to allow the usage of Atom feeds with multiple links for each item, but the variable captures RSS feeds that have multiple links for a feed as well. It's not really useful for JSON, but it still captures the single link as one would expect.

[coveralls]

Coverage increased (+0.4%) to 74.568% when pulling d407d33 on makeworld-the-better-one:master into 68eef24 on mmcdole:master.

[makew0rld]

@mmcdole All tests now pass, and all merge conflicts have been resolved. Can this be merged? Thanks!

[ecliptik]

@mmcdole ping if this could get reviewed and merged as it would help with some Debian packaging too. Thank you.

[nileshpatra]

@mmcdole ping again. This is really important for us. I'd really appreciate if you could merge this and if possible tag a patch/minor release.
This would help unblock a bunch of packaging work

[mmcdole]

@nileshpatra @ecliptik would #153 also solve this for you?

[makew0rld]

@mmcdole Thanks for responding. I don't think so? It doesn't look like that supports multiple Atom links.

[nileshpatra]

@mmcdole @drakenot I agree with makeworld there, it likely won't

[Necoro]

Chiming in here too: No, the two PRs are orthogonal.

[mmcdole]

Thanks everyone. I see now that this was adding it to Atom as well.

I knew that @Necoro's PR allowed the parsing of Atom elements in the RSS feed. I didn't want a one-off Atom element in RSS if there was a way to parse any atom element within an RSS feed.

[makew0rld]

Thank you for merging!

To others: Amfora has updated in makew0rld/amfora@6fa3600