v0.8-2

This is a major enhancement release of the vcdExtra package, focusing on documentation and examples.

• added HouseTasks data set, illustrating permutation of row / col variables
• package now depends on R (>= 3.5.0) per CRAN nit
• add Suggests: seriation to illustrate CA re-ordering of rows/cols based on correspondence analysis
• all .Rd files reformatted and many examples extended.
• the vignette mosaic.Rmd on mosaic displays has been extensively revised with examples for square tables and permutation of row / column variables.
• begin to classify datasets with \concept{} tags
• Added a new demo-housing.Rmd vignette, using content from demo/housing.R.