Consecutive reference links without link identifiers are not recognized

[nchammas]

This is a clone of the issue originally reported here: gettalong/kramdown#538

This block of Markdown

[eeny] [meeny] [miny] [moe]

[eeny]: http://example.com
[meeny]: http://example.com
[miny]: http://example.com
[moe]: http://example.com

renders all four links here on GitHub as well as on CommonMark's parser:

eeny meeny miny moe

However, Kramdown renders it as:

eeny miny

I don't know if the Kramdown project is interested in tracking GitHub or CommonMark's behavior that closely, but at least from a naive user perspective, I think their behavior is more intuitive than Kramdown's.