Error(s) in re-building vignettes:
  ...
--- re-building ‘classes.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) and/or pandoc-citeproc not available. Falling back to R Markdown v1.
Quitting from lines 44-52 (classes.Rmd) 
Error: processing vignette 'classes.Rmd' failed with diagnostics:
there is no package called 'kableExtra'
--- failed re-building ‘classes.Rmd’

--- re-building ‘kable.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) and/or pandoc-citeproc not available. Falling back to R Markdown v1.
Quitting from lines 62-69 (kable.Rmd) 
Error: processing vignette 'kable.Rmd' failed with diagnostics:
there is no package called 'kableExtra'
--- failed re-building ‘kable.Rmd’

--- re-building ‘rmarkdown.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) and/or pandoc-citeproc not available. Falling back to R Markdown v1.
--- finished re-building ‘rmarkdown.Rmd’

--- re-building ‘slickr.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) and/or pandoc-citeproc not available. Falling back to R Markdown v1.
Quitting from lines 46-50 (slickr.Rmd) 
Error: processing vignette 'slickr.Rmd' failed with diagnostics:
R: delegate failed `'potrace' --svg --output '%o' '%i'' @ error/delegate.c/InvokeDelegate/1958
--- failed re-building ‘slickr.Rmd’

--- re-building ‘tests_and_coverage.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) and/or pandoc-citeproc not available. Falling back to R Markdown v1.
--- finished re-building ‘tests_and_coverage.Rmd’

--- re-building ‘tex_packages.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) and/or pandoc-citeproc not available. Falling back to R Markdown v1.
--- finished re-building ‘tex_packages.Rmd’

--- re-building ‘tikz.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) and/or pandoc-citeproc not available. Falling back to R Markdown v1.
--- finished re-building ‘tikz.Rmd’

SUMMARY: processing the following files failed:
  ‘classes.Rmd’ ‘kable.Rmd’ ‘slickr.Rmd’

Error: Vignette re-building failed.
Execution halted