Openslide-python

* Fix documentation build breakage

* Add documentation
* Switch from distutils to setuptools
* Declare Pillow dependency in `setup.py` (but still support PIL)

* Fix breakage on Python 2.6
* examples: Fix tile server breakage on classic PIL

* Require OpenSlide 3.4.0
* Support Python 3
* Return Unicode strings on Python 2
* Replace `OpenSlide.can_open()` with `OpenSlide.detect_format()`
* Optionally generate Deep Zoom tiles only for the non-empty slide region
* Fix Deep Zoom tile positioning bug affecting Aperio slides
* Fix library loading with MacPorts
* Propagate open errors from `openslide.open_slide()`
* examples: Add multiple-slide Deep Zoom server
* examples: Enable multithreading in tile servers
* examples: Avoid loading smallest Deep Zoom levels
* examples: Update OpenSeadragon to 1.0.0

* Require OpenSlide 3.3.0
* Rename `layer` to `level` throughout API
* Provide OpenSlide version in `openslide.__library_version__`
* Properly report `openslide_open()` errors on OpenSlide 3.3.0
* Fix library loading on Mac OS X

* Fix segfault if properties/associated images accessed after `OpenSlide`
is closed
* Add methods to get Deep Zoom tile coordinates and dimensions
* Fix loading libopenslide on Windows
* Fix for large JPEG tiles in example Deep Zoom tilers
* Make example static tiler output self-contained