sgplot 0.4.0

• use_sgplot() gains a palette_type argument to set default palette type
  for geoms. The default value is "sg" to use Scottish Government colour palettes.
  To use the Social Security Scotland palette type, for example, use:
  use_sgplot(palette_type = "sss") (#34).

• The default_colour argument of use_sgplot() is deprecated in favour of the
  palette_type argument (#34).