Do cleanup on insert/delete/sdt tags

[jlward]

• Until we actually start using them remove the author/date attributes.
• Do not break separate insert, delete or sdt tags in lists or tables.

[winhamwr]

And when you do add them back in, I'd say they should be something like data-pdx-author and data-pdx-date

[jlward]

Also handle sdt tags as well.

[winhamwr]

Looks solid.