pocount: use mutually exclusive group for argparse
pocount: use argparse to handle --incomplete
pocount: use argparse to select the chosen style
docs: make doc options match --help
Identify the index by identity rather than __eq__
Fix off-by-one

This was giving an index beyond the length of `before`.
Correctly insert at an existing parent if appropriate

At the end of a string (Case 2) the undo of a deletion of a placeable
(e.g. an XML tag) would be restored as plain text instead of part of
the existing tag.
Revert "Correctly insert at an existing parent if appropriate"

This reverts commit bb04ce073bfd5e1543285074b20fedf54d3f6feb.

Tests are failing because of this change. Nothing seems wrong with the
change but it needs a fix to the related tests before it lands again.
docs: add ref for intersphinx links
roundtrip: run silently when roundtripping
dtd: underscore is valid in entity names

We where failing is_valid_accesskey when entity name contained _ which
would remove a leading & and make the entity invalid.
dtd: optional expected makes cleaner roundtrip setups
accesskeys: test numeric keys
accesskeys: test combining non-ASCII keys

The function actually claimed to return Unicode but was converting to a
basestring.  So this also drops that conversion to basestring.
misc: Drop diff_match_patch

Since it is not used anywhere within TTK itself, the requirement can be
dropped entirely
req: eliminate min-required.txt
req: sort requirements lists
py3: Add six to dependencies
py3: Fix html-related imports on Python 3
cleanup: Replace dictutils.ordereddict by collections.OrderedDict