Xmldiff

------------------

- Added options for faster node comparisons. The "middle" option is now
default, it had very few changes in matches, but is much faster.

- Implemented a Fast Match algorithm for even faster diffing.

- Speed improvements through caching

- Fixed a bug where MoveNode actions sometimes was in the wrong order

- Added an InsertComment action, as comments require different handling,
so it's easier to deal with them this way. You can still use DeleteNode and
UpdateTextIn for them with no special handling.

- When renaming tags the XMLFormatter will mark them with "diff:rename"
instead of making a new tag and deleting the old.

- Tags will now be moved first, and updated and renamed later, as the new
tag name or attributes might not be valid in the old location.

----------------

- A complete, bottom-up, pure-python rewrite

- New easy API

- 100% test coverage

- New output formats:

- A new default output format with new actions

- A format intended to be parseable by anyone parsing the old format.

- XML with changes marked though tags and attributes

- xmldiff 2.0 is significantly slower than xmldiff 0.6 or 1.0,
the emphasis so far is on correctness, not speed.


- Added option to XMLFormatter to use replace tags

- in _make_diff_tags after diffing, neighboring delete/insert diffs are joined to a replace tag

- the deleted text is added as an attribute ("old-text")

- the inserted text is the element's text