Bump version

I'm still stuck on a version that's 1.5 years old!

Author: jthemphill

rust-mode.el

@@ -1,6 +1,6 @@
 ;;; rust-mode.el --- A major emacs mode for editing Rust source code -*-lexical-binding: t-*-
 
-;; Version: 0.3.0
+;; Version: 0.4.0
 ;; Author: Mozilla
 ;; Url: https://github.com/rust-lang/rust-mode
 ;; Keywords: languages