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

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