Add failing tests and then fix them. Use a common function to DRY in
all the modules.

Fixes #78

Also use zope.testrunner in tox (and travis) because it allows passing
arguments to select what tests to run, see slow tests, etc.

Simplify setup.py to always build the C modules and avoid polluting
wheel caches (the same as zope.security and other projects that have
been worked on lately).

Bump the minimum 'persistent' requirement to one that actually works
in PURE_PYTHON mode (plus fix wheel metadata; otherwise we need
environment markers).

Test PURE_PYTHON in environments on Travis. Do some minor tuning to
eliminate redundant test cases and speed up test time.

Fix possibility of rare crash during dealloc. Fixes #75

cleanup after manylinux wheelbuilding

errant white space preventing some builds in manylinux

Build and deploy manylinux builds on tagged commit

Add documentation for Length class

Conflicts:
	CHANGES.rst
	setup.py

I tried to tighten the whitelist, but that didn't work.

distutils must die.

Work around AttributeError raised by Python 3.5.x.

Alternative to PR #55.

* Use macpython everywhere.

Add 3.6 for mac.

See zopefoundation/persistent#59

* Manually install persistent for travis.

* plain pypy3 is python 3.2 which won't run newer setuptools

Add support for Python 3.6

Allow None as a special key (sorted smaller than all others).

Cuz the complicated version was wrong, in addition to being complicated :)

Also removed s stupid non-optimization in compare

Python/C OO consistency

Check key identity before ==. This matches the C implementation.
Fixes #50

Add a pickle test to the work done in #54. Fixes #51. Fixes #53 (for
Python 2).

Check for object key default comparison on set only