Toyplot 0.17.0

• Moved sample datasets into the toyplot.data module.
• toyplot.mp4.render() generates H.264 output.
• Restored toyplot.canvas.AnimationFrame.set_datum_text(), which was with the debut of rich text..
• Use the Python warnings module for deprecation warnings.
• Disabled pylint testing on Travis-CI, it was too much of a moving target.
• Simplified the animation API.
• Switched to Python 3 as the primary build and test environment.
• Removed obsolete dependencies from the Travis build.
• Disabled PNG downscaling for ghostscript versions < 9.14.
• Table cell data can be rotated.
• Moved image manipulation into a new toyplot.bitmap module.
• Added a bitdepth option to toyplot.bitmap.to_png().
• Allow default canvas width and height to be set in toyplot.config.
• Fixed a false-positive comparing XML documents.
• Explicit colormap domains aren't required for toyplot.canvas.matrix().