Bump version to 0.4.0

This change bumps the version of the crate to 0.4.0. The following
notable changes have been made since 0.3.5:
- Added support for the Librem Key
- Added support for user provided extensions through lookup via the
  PATH environment variable
- Added the fill command that fills the SD card of a Nitrokey Storage device
  with random data
  - Added the termion dependency in version 1.5.6
- Added SD card usage information to the output of the status command for
  Storage devices
- Renamed the --{no-,}{numlock,capslock,scrollock} options of the config
  set command to --{no-,}{num-lock,caps-lock,scroll-lock}
- Added support for generating completion scripts for shells other than
  bash
- Bumped anyhow dependency to 1.0.39
- Bumped libc dependency to 0.2.90
- Bumped nitrokey dependency to 0.8.0
- Bumped serde dependency to 1.0.118
- Bumped structopt dependency to 0.3.21
- Bumped toml dependency to 0.5.8
- Bumped various transitive dependencies to most recent versions

Author: d-e-s-o

CHANGELOG.md

@@ -1,5 +1,5 @@
-Unreleased
-----------
+0.4.0
+-----
 - Added support for the Librem Key
 - Added support for user provided extensions through lookup via the
   `PATH` environment variable

Cargo.lock

@@ -5,7 +5,7 @@
 
 [package]
 name = "nitrocli"
-version = "0.3.5"
+version = "0.4.0"
 edition = "2018"
 authors = ["Daniel Mueller <[email protected]>"]
 license = "GPL-3.0-or-later"