Error(s) in re-building vignettes:
  ...
--- re-building ‘models-from-other.Rmd’ using rmarkdown
trying URL ‘http://ryantimpe.com/files/mf_unicorn.PNG’
Warning in download.file("http://ryantimpe.com/files/mf_unicorn.PNG", demo_img,  :
  URL ‘http://ryantimpe.com/files/mf_unicorn.PNG’: status was ‘Couldn't resolve host name’
Quitting from lines 34-41 (models-from-other.Rmd) 
Error: processing vignette ‘models-from-other.Rmd’ failed with diagnostics:
cannot open URL ‘http://ryantimpe.com/files/mf_unicorn.PNG’
--- failed re-building ‘models-from-other.Rmd’

--- re-building ‘models-from-program.Rmd’ using rmarkdown
--- finished re-building ‘models-from-program.Rmd’

--- re-building ‘models-from-tables.Rmd’ using rmarkdown
--- finished re-building ‘models-from-tables.Rmd’

--- re-building ‘models-piece-type.Rmd’ using rmarkdown
--- finished re-building ‘models-piece-type.Rmd’

--- re-building ‘mosaics.Rmd’ using rmarkdown
trying URL ‘http://ryantimpe.com/files/mf_unicorn.PNG’
Content type 'image/png' length 277758 bytes (271 KB)
==================================================
downloaded 271 KB

[WARNING] Could not fetch resource http://ryantimpe.com/files/mf_unicorn.PNG: HttpExceptionRequest Request {
    host                 = "ryantimpe.com"
    port                 = 80
    secure               = False
    requestHeaders       = []
    path                 = "/files/mf_unicorn.PNG"
    queryString          = ""
    method               = "GET"
    proxy                = Nothing
    rawBody              = False
    redirectCount        = 10
    responseTimeout      = ResponseTimeoutDefault
    requestVersion       = HTTP/1.1
    proxySecureMode      = ProxySecureWithConnect
  }
   (ConnectionFailure Network.Socket.getAddrInfo (called with preferred socket type/protocol: AddrInfo {addrFlags = [], addrFamily = AF_UNSPEC, addrSocketType = Stream, addrProtocol = 0, addrAddress = 0.0.0.0:0, addrCanonName = Nothing}, host name: Just "ryantimpe.com", service name: Just "80"): does not exist (Try again))
--- finished re-building ‘mosaics.Rmd’

SUMMARY: processing the following file failed:
  ‘models-from-other.Rmd’

Error: Vignette re-building failed.
Execution halted