Replace directories with platform_dirs create

`directories` create is no longer maintained, and uses
`~/Library/Preferences` on MacOS, but Apple advises against creating
files in `Preferences`.

`platform-dirs` allows to use `~/.config` on MacOS.

src/main.rs

@@ -4,7 +4,6 @@ extern crate crossbeam_channel;
 extern crate cursive;
 #[cfg(feature = "share_clipboard")]
 extern crate clipboard;
-extern crate directories;
 extern crate failure;
 extern crate futures;
 #[macro_use]