First attempt at supporting Pandoc-style footnotes. The existing tests have not broken but the new functionality does not work yet.
new tests pass but old tests now fail...
Referenced footnotes appear to be functional. Inline still unimplemented.
Implementation and some tests for inline footnotes. Also I noticed the list items had the wrong ids, that was silly of me.
added slice bounds check
leftover debug stuff
parser no longer returns prematurely from empty footnote ref
Merge pull request #27 from moshee/master

Footnotes (addresses #14)