v0.9.4

AlgebraOfGraphics v0.9.4

Diff since v0.9.3

Merged pull requests:

• Add penguins testdata (#613) (@jkrumbiegel)

Closed issues:

• Mapping :marker with visual contour raises an ArgumentError (#604)
• Include other tutorials in the new docs (#605)
• Adding text/annotations to a heatmap (a recipe ?) (#606)