update to rust edition 2018 + bump version

Cargo.toml

@@ -2,12 +2,13 @@
 name = "ncspot"
 description = "ncurses Spotify client written in Rust using librespot, inspired by ncmpc and the likes."
 exclude = ["screenshots/**"]
-version = "0.1.2"
+version = "0.1.3"
 authors = ["Henrik Friedrichsen <henrik@affekt.org>"]
 repository = "https://github.com/hrkfdn/ncspot"
 keywords = ["spotify", "ncurses", "librespot"]
 license = "BSD-2-Clause"
 readme = "README.md"
+edition = "2018"
 
 [badges]
 travis-ci = { repository = "hrkfdn/ncspot", branch = "master" }