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

Point the doc link to the rendered site.

Mostly for PyPI benefit.

[skip ci]

Add requirements file for RTD.

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.