o Warn when offset results in empty polygon.
Merge remote-tracking branch 'upstream/master'
o Gnuplot is confused with newlines. Make that hashes.
Merge branch 'master' of github.com:hzeller/gcode-multi-shell-extrude
o add gnuplot tip.
o Link hilbert sample file.
o fix link
Merge remote-tracking branch 'upstream/master'
o Simple brim feature.
o Improved algorithm to find the start-point of an offset
  polygon. Now we are not only looking for the closest to the start-point,
  but it should be closest to the line defining the direction (which is a more
  accurate way to see this)
o Show different colors for Brim vs. not
o Make postscript-lines only 0.8 * shell-thickness to be able to
  see the spiral brim.
o Made spiral distance a bit less for better overlap.
o Make brim spiral thickness configurable.
o rename option.
o experimental brim-smooth radius
o Initial starting shell thick factor of 0.7 seems to be better in
  practice. More overlap.
o fix broken offset calculation.
o Tweaking of brim layer height and factor.
o Make it simpler to twiddle PostScript output to better
  see lines.
o Tweak accuracy parameters.
o Spiral: scale from centroid point.