More consistency between Python and C impls.

Fixes #42.

See CHANGES.rst for details on what changes. Additional test cases cover
the changed behaviour.

build BTrees for 3.4

The wineggbuilder does that already.  Eventually, we will drop building them altogether, and when we do, it will be easier to just decommission that machine.

attempt to fix pypi password

install zodb to make sure those dependent tests are run

Use unittest.skip to skip tests

This way skipped tests will be visible in the test runner output.

Add Travis and AppVeyor build badges

(Try to) fix appveyor build

Replace with 'PyLong_AsLongLongOverflow'.

Toward a fix for #32.

See: https://github.com/zopefoundation/BTrees/issues/32.

Don't use/poison global wheel cache when building w/ PURE_PYTHON.

Introduced in PR #20, they get tested via the 'py27-pure' tox environment.

build os x wheels and deploy to pypi

Conflicts:
	.travis.yml

Drop support for Python 2.6 and 3.2.

- 2.6 is long out-of-maintenance, and a security quagmire.

- 3.2 cannot be tested on Travis.