Reformat commit HTML

- Make Repository name in caption a link to repo
- Less testing for <thead> & <tfoot>
- SHA in a <data>, and trim the visible width to 8 characters
- Commit message now in <samp>
- Commit author is no a `mailto:` link, including subject
- Output start and end positions at bottom of table
Style for [rel=next] & [rel=prev]

Set size to 1 rem, colro to --alt-color, font to --icon-font, &
set content as appropriate for font