ggforce 0.3.0

• Added facet_matrix() in order to facet different data columns into different
  rows and columns in a grid, in order to make e.g. scatterplot matrices and
  pairs plot
• Added geom_autopoint() and position_auto() to jitter points based on the
  type of positional scales in the panel
• Added geom_autohistogram() and geom_autodensity() for facilitating
  distribution plots along the diagonal in a facet_matrix() plot.
• Added facet_row() and facet_col to have one-dimensional facet_wrap()
  with possibility of variable sizing.
• Stats should now always keep the old group variable (potentially with
  something added), making them work with gganimate
• Removed the Visual Guide vignette to reduce compilation time. See the
  website for an overview of all functionality with compiled examples
  (https://ggforce.data-imaginist.com)