feat(rust-setup): Add Rust setup

Adds a simple Rust setup with autocompletion via Racer and built-in
Cargo command support.

init.el

@@ -17,6 +17,7 @@
     ace-jump-mode
     ag
     browse-kill-ring
+    cargo
     confluence
     dash
     dockerfile-mode
@@ -38,6 +39,7 @@
     password-store
     pkgbuild-mode
     puppet-mode
+    racer
     rainbow-delimiters
     rainbow-mode
     rust-mode

init/rust-setup.el

@@ -0,0 +1,14 @@
+(require 'rust-mode)
+
+;; Enable cargo-related (C-c C-c C-...) commands.
+(add-hook 'rust-mode-hook #'cargo-minor-mode)
+
+;; Configure autocompletion for rust
+(add-hook 'rust-mode-hook #'racer-mode)
+(add-hook 'racer-mode-hook #'company-mode)
+(add-hook 'racer-mode-hook #'eldoc-mode)
+(define-key rust-mode-map (kbd "TAB") #'company-indent-or-complete-common)
+(setq company-tooltip-align-annotations t)
+
+;; Ensure long compiler errors don't flow out of the screen (very annoying!)
+(add-hook 'cargo-process-mode-hook #'visual-line-mode)