Refactor shell setup into ~/.zshenv and ~/.zshrc files

It was time to split the environment related stuff out to ~/.zshenv,
leaving my ~/.zshrc file specifically for setup of interactive shells.

zsh/docker.zsh

@@ -7,5 +7,5 @@ alias dc="docker-compose"
 alias co="docker-compose"
 
 docker_remove_exited () {
-  docker rm $(docker ps -f="status=exited" -q)
+  docker rm "$(docker ps -f='status=exited' -q)"
 }