Individual cite links

[sneakers-the-rat]

Fix #352

This isn't done, and probably isn't the best way to do this, but figured id open it as a starting point instead of just sitting on it in my fork.

this renders group citations with individual links to each of their cites like this (red border added to accentuate their being separate links)

what it doesn't do is handle styles that would want to render [1-4], but i figured you'd know how to handle that better than i do - i tried to walk up through citeproc to see if i could mimic the process of joining multiple rendered citations, but i couldn't find it. reading ruby is still sort of hard to me, never sure where things get defined.

but if we like this general approach and you have some guidance on how to get that problem resolved, i'll write tests and finish this up

[sneakers-the-rat]

I don't really understand the windows test failures here, it looks like they're just failing to load the bibliography and instead returning missing_reference, however the leg of the cite method that returns missing_reference is outside the changes made in this PR - i.e. this PR doesn't change the path that would be taken to get to missing_reference, so i'm not quite sure if/how i caused those failures.

[inukshuk]

Thanks! The Windows issues are indeed unrelated.