forgot to export dir_create()

no longer show the meaningless number of downloads, but just show the latest CRAN version instead

CRAN release v0.19

mention the option xfun.bg_process.verbose

add a function `is_web_path()` to test if a path is a web path that starts with `http://` or `https://` or `ftp://` or `ftps://`

rename the first argument from 'path' to 'x' to be consistent with other path functions