fix for encoding in base64_to_df

[andreasio]

With a simple "encoding" added, we can tell R to encode in UTF-8.

base64_to_df <- function(x) {
  raw_csv <- rawToChar(base64enc::base64decode(x))
  return(read.table(textConnection(raw_csv), stringsAsFactors = FALSE, header=TRUE,
                  sep = ";", encoding = "UTF-8" ))
}