v0.6.0

Added

• In weasysvg.portable(), no opacity level of a gradient is narrower than band_px CSS px of the drawing as
  shown, 1 by default, where its opacity changes most slowly. A small gradient gets fewer levels: a level per
  1/64 was a third of a pixel over 20 px, and the flat SVG drew each one in full. weasysvg-convert --band-px
  and to_svg(band_px=) set it; 0 keeps a level per 1/64.
• The levels of a blur in weasysvg.portable() follow band_px too: where the softest blurred edge rises
  fastest, its contours lie at least band_px apart. A blur of 4 px takes 10 levels, not 64. The flat SVG of
  the corpus shrinks from 261 MB to 25 MB and flattens in 6.4 s, not 84 s: Tux from 244 MB, which librsvg
  refused to draw, to 12.9 MB, the Inkscape logo from 3.0 MB to 1.0 MB. Against the PDF none drifts further.
• Both measure a length as shown along its own direction: a transform that stretches one axis and squeezes
  the other keeps the levels along the stretched one.

Fixed

• The flat SVG of weasysvg-convert writes each clip path once. cairo wrote the clip of a shape again for every
  paint inside it, and a gradient with a transparent stop is painted once per opacity level: the OpenStreetMap
  logo came out at 29 MB, now 9.6 MB, and Word slowed down on it.

Full changelog: v0.5.0...v0.6.0