System.File: fix mkdir_nothrow()
System.File: add redraw in copy/move
System.File: update document
System.File: use system() instead of :!
Data.String: Add levenshtein_distance({str1}, {str2}) function.
Merge pull request #168 from kamichidu/levenshtein_distance

Data.String: Add levenshtein_distance({str1}, {str2}) function.
System.File: use system() instead of :!, thx @mattn
System.File: add /y option to move command
System.File: move(): use move_exe() when a:src is directory

Currently s:move_vim() does not support
moving a directory.
System.File: fix filepaths to suit for copy command
Merge branch 'sys.file' into merge-sys-file

Conflicts:
	autoload/vital/__latest__/System/File.vim