automatically detect orientation in geoms

[mjskay]

• [x] auto-detect orientation in slabinterval stats and geoms
• [x] auto-detect orientation in lineribbon stats and geoms
• [x] drop .lower and .upper auto-mappings from non-horizontal shortcut geoms
  • [x] default_mapping
  • [x] add_default_computed_aesthetics - drop from lineribbon?
• [x] deprecate all "h"-suffix geoms
  • [x] simplify tests
• [x] might as well finally add deprecation warning to geom_eye etc too
• [x] update vignettes and examples
  • [x] remove refs to horizontal geoms
  • [x] remove refs to ggstance
  • [x] freq-uncertainty-vis.Rmd
  • [x] tidybayes-residuals.Rmd
  • [x] tidybayes.Rmd
  • [x] tidy-rstanarm.Rmd
  • [x] slabinterval.Rmd
  • [x] README.Rmd
  • [x] tidy-brms.Rmd
  • [x] tidy-rethinking.Rmd
  • [x] double-check function examples
  • [x] strings to search: [h], [h|]
  • [x] regexes: (stat|geom)_\w*h\b, (Stat|Geom)\w*h\b