Yihui Xie (9):
      close #83: move knitr::imgur_upload() to xfun::upload_imgur()
      forgot to suggest xml2 in the previous commit
      use R Markdown v1 for vignette
      shouldn't paste() here because `code` could be a vector of length > 1, and each line may be an incomplete expression
      update packages only in libraries that are writable by the current user
      close yihui/knitr#2331: provide a fenced_block() function to be reused in knitr and possibly pandoc/litedown
      add {} if any attribute contains =
      add a test for 5a63018c7cd9e31e84168536825bdf9d02d54215
      CRAN release v0.43