Use tablenotes and tnote to allow footnotes with references?

[hughjonesd]

This would let users do e.g.

add_footnote(1, 3, "Footnote for row 1 column 3")

and would create a subscript in the appropriate place. tablenotes and footnotes are defined by threeparttable. HTML et al. might not be so easy. HTML has the <tfoot> tag.