OpenSlide Python 0.5.0

• 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