Major reorganization of implementation. The two-level ``Options``
and ``OptionsChain`` strategy replaced with single-level
``Options`` based directly on ``ChainMap`` (or more precisely, on
an attribute-accessible subclass of it). It's now turtles all the
way down.
Systematic enough change that by traditional versioning standards
this would be a 2.0 release. But following Semantic Versioning,
while the class structure changes, the effective API seen by using
modules does not change, so 1.4.0 is enough.
Correctness of this systematic roto-tilling confirmed by test
suite. Testing now extended to 100% line coverage (and 99% branch
coverage). Some edge case issues were discovered and corrected.
Thank you to coverage testing for ferreting those out.
No longer depends on `stuf <https://pypi.python.org/pypi/stuf>`_.
Coupled with a new supporting `chainmap
<https://pypi.python.org/pypi/chainmap>`_ polyfill, decisively
returns compatibility for Python 2.6 in a way that doesn't depend
on the release schedule or priorities of external modules.