Optionally use `fwrite()` instead of `write.table()` for `write_ascii()`

To improve speed. May work like so:

``` r 
data.table::fwrite(
  x = data,
  file = path,
  sep = "\t",
  dec = dec,
  col.names = TRUE,
  row.names = FALSE,
  quote = FALSE,
  fileEncoding = "UTF-8"
)
```