Release 2.3.1

[Argmaster]

Release 2.3.1

• Added support for rotation of code 21 center line macro primitive in SVG and Raster
  renderers. Support is not exhaustive, it will be extended whenever extension is
  requested by users.
• Fixed bug causing macro flashes to be partially cut off in images rendered with SVG
  renderer.
• Fixed incorrect version string in pygerber.__version__ and reported by
  pygerber --version.