Pytool

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- Add :class:`pytool.time.Timer` for easy timing of things.

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- Fix bug with setup.py which broke installs.

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- Changed to depend on simplejson (``>=3.2.0``) for the ``_asdict()`` and
``for_json()`` hooks. This may break backwards compatability.

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- Fix bug where ``for_json()`` hook was ignored on classes that subclass the
basic types.
- Fix bug where :func:`pytool.json.as_json` would leave a trailing space on
timestamps if there is no timezone associated with them.

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- Improve documentation.
- Add ``for_json()`` hook in :func:`pytool.json.as_json`.
- Add ``__repr__()`` to :class:`pytool.time.UTC` to make it prettier.
- Add support for ``_asdict()`` hook (implemented by :class:`namedtuple`) even
when not using :mod:`simplejson`.
- Fix :func:`pytool.time.is_dst` test.
- Add ``for_json()`` hook to :class:`pytool.proxy.DictProxy` and
:class:`pytool.proxy.ListProxy`.

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- Fix descriptor protocol in iteritems.