Like FS streams, but with stat on them, and supporting directories and
symbolic links, as well as normal files. Also, you can use this to set
the stats on a file, even if you don't change its contents, or to create
a symlink, etc.

So, for example, you can "write" a directory, and it'll call mkdir. You
can specify a uid and gid, and it'll call chown. You can specify a
mtime and atime, and it'll call utimes. You can call it a symlink
and provide a linkpath and it'll call symlink.

Note that it won't automatically resolve symbolic links. So, if you
call fstream.Reader('/some/symlink') then you'll get an object
that stats and then ends immediately (since it has no data). To follow
symbolic links, do this: fstream.Reader({path:'/some/symlink', follow: true }).

There are various checks to make sure that the bytes emitted are the
same as the intended size, if the size is set.

Examples

 fstream
  .Writer({ path: "path/to/file"
          , mode: 0755
          , size: 6
          })
  .write("hello\n")
  .end()

This will create the directories if they're missing, and then write
hello\n into the file, chmod it to 0755, and assert that 6 bytes have
been written when it's done.

 fstream
  .Writer({ path: "path/to/file"
          , mode: 0755
          , size: 6
          , flags: "a"
          })
  .write("hello\n")
  .end()

You can pass flags in, if you want to append to a file.

 fstream
  .Writer({ path: "path/to/symlink"
          , linkpath: "./file"
          , SymbolicLink: true
          , mode: "0755" // octal strings supported
          })
  .end()

If isSymbolicLink is a function, it'll be called, and if it returns
true, then it'll treat it as a symlink. If it's not a function, then
any truish value will make a symlink, or you can set type: 'SymbolicLink', which does the same thing.

Note that the linkpath is relative to the symbolic link location, not
the parent dir or cwd.

 fstream
  .Reader("path/to/dir")
  .pipe(fstream.Writer("path/to/other/dir"))

This will do like cp -Rp path/to/dir path/to/other/dir. If the other
dir exists and isn't a directory, then it'll emit an error. It'll also
set the uid, gid, mode, etc. to be identical. In this way, it's more
like rsync -a than simply a copy.