------------------
- Fix a potential rare crash when deallocating proxies. See `issue 20
<https://github.com/zopefoundation/zope.proxy/issues/20>`_.
- Drop support for Python 3.3.
- Drop support for "python setup.py test".
- 100% test coverage.
- Fix indexing pure-Python proxies with slices under Python 3, and
restore the use of ``__getslice__`` (if implemented by the target's
type) under Python 2. Previously, pure-Python proxies would fail
with an AttributeError when given a slice on Python 3, and on Python
2, a custom ``__getslice__`` was ignored. See `issue 21
<https://github.com/zopefoundation/zope.proxy/issues/21>`_.