linking to footnotes, with some formatting

Footnotes are now superscript with link to notes at end.  I did this with vim find/replace... if you want different formatting it is easy to adjust which I did in two sections:
```
%s/ *\[\^\([^]]*\)]/<sup>\[\1](#footnote-\1)<\/sup>/g  
%s/ *\[\^\([^]]*\)]/<sup><a id="footnote-\1">\1<\/a><\/sup>/g
```