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- Add support for PyPy and PyPy3.
- Add support for Python 3.4.
- BTree subclasses can define ``max_leaf_size`` or ``max_internal_size``
to control maximum sizes for Bucket/Set and BTree/TreeSet nodes.
- Detect integer overflow on 32-bit machines correctly under Python 3.
- Update pure-Python and C trees / sets to accept explicit None to indicate
max / min value for ``minKey``, ``maxKey``. (PR 3)
- Update pure-Python trees / sets to accept explicit None to indicate
open ranges for ``keys``, ``values``, ``items``. (PR 3)