Error(s) in re-building vignettes:
  ...
--- re-building ‘authentication.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 ‘authentication.Rmd’

--- re-building ‘geocoder.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 57-64 (geocoder.Rmd) 
Error: processing vignette 'geocoder.Rmd' failed with diagnostics:
cannot open the connection
--- failed re-building ‘geocoder.Rmd’

--- re-building ‘intermodal.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 58-65 (intermodal.Rmd) 
Error: processing vignette 'intermodal.Rmd' failed with diagnostics:
cannot open the connection
--- failed re-building ‘intermodal.Rmd’

--- re-building ‘routing.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 49-59 (routing.Rmd) 
Error: processing vignette 'routing.Rmd' failed with diagnostics:
cannot open the connection
--- failed re-building ‘routing.Rmd’

--- re-building ‘traffic.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 41-49 (traffic.Rmd) 
Error: processing vignette 'traffic.Rmd' failed with diagnostics:
cannot open the connection
--- failed re-building ‘traffic.Rmd’

--- re-building ‘transit.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 56-62 (transit.Rmd) 
Error: processing vignette 'transit.Rmd' failed with diagnostics:
cannot open the connection
--- failed re-building ‘transit.Rmd’

--- re-building ‘weather.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 54-70 (weather.Rmd) 
Error: processing vignette 'weather.Rmd' failed with diagnostics:
cannot open the connection
--- failed re-building ‘weather.Rmd’

SUMMARY: processing the following files failed:
  ‘geocoder.Rmd’ ‘intermodal.Rmd’ ‘routing.Rmd’ ‘traffic.Rmd’
  ‘transit.Rmd’ ‘weather.Rmd’

Error: Vignette re-building failed.
Execution halted