add some developer-readme notes
note explicitly the Python versions we support
Add an icon for Lasercake (Eli's creation).

The means of turning the SVG into ico (Windows) and icns (OS X)
are documented in the website repo; copying the Python here
just in case it gets lost:

resolutions = ('8x8', '16x16', '32x32', '64x64', '128x128', '256x256', '512x512', '1024x1024')
for res in resolutions:
        # I couldn't get imagemagick to create partial png transparency
        # out of an SVG, but inkscape happily does it:
        os.system(r"""inkscape --without-gui --export-png=tmp/uncrushed-icon-{0}x{1}.png --export-background-opacity=0 -w {0} -h {1} src/icon.svg""".format(*res.split('x')))
        # pngcrush, in addition to shrinking the file size,
        # removes EXIF image metadata.  It's a good thing
        # that it gets rid of the DPI metadata.
        os.system(r"""pngcrush -q tmp/uncrushed-icon-{0}.png compiled/_cacheable/icon-{0}.png""".format(res))

# For the Windows binary.
subprocess.call(['convert']
        + ['compiled/_cacheable/icon-{0}.png'.format(res) for res in resolutions]
        + ['compiled/misc/icon-multires.ico'])

# ICNS is the OS X icon format.  png2icns of `libicns` is the only
# FOSS/cross-platform software I found to create them.  Its current
# version (0.8.1) doesn't support the @2x retina icon components but
# does support sizes up to 1024x1024 pixels.   Apple's `iconutil` is
# OS X 10.7+, which does not include 10.6, Linux, or Windows.
# '64x64' is not a component of ICNS files, so we explicitly list the
# resolutions.
subprocess.call(['png2icns', 'compiled/misc/icon-multires.icns']
        + ['compiled/_cacheable/icon-{0}.png'.format(res) for res in
        ('16x16', '32x32', '128x128', '256x256', '512x512', '1024x1024')])
Attempt to add the icon to the binary for Windows and Mac.