Incorrect 'footnote' link conversion

[zaus]

When links are "footnoted" (i.e. entered as [This is a link][], potentially in multiple places, with the link later as [This is a link]: http:/...) it does not correctly match them back inline.

[benbalter]

The converter as currently written only supports inline links, although it doesn't necessarily have to be that way.

Would gladly accept a pull request to add this feature if you are able to.

[zaus]

I'll try to get around to it... I bet it'll starts with the regex \[([^\]]+)\]\[\]...