Release 1.4.3

This is the last planned bug-fix release in the 1.4 series.

Many bugs are fixed including:

• fixing drawing of edge-only markers in AGG
• fix run-away memory usage when using %inline or saving with
  a tight bounding box with QuadMesh artists
• improvements to wx and tk gui backends

Additionally the webagg and nbagg backends were brought closer to
feature parity with the desktop backends with the addition of keyboard
and scroll events thanks to Steven Silvester.