1.4.0

• Setup Arduino development
• Update documentation
• Remove rustfmt package (now in rust-mode)
• Add spaceline for modeline
• Improve UI using mode-icons
• Update OCaml configuration and dependencies
• FIX CircleCI configuration
• Update Gnus configuration for GMail
• Add hydra for golang and python
• FIX Haskell configuration
• FIX projectile completion backends