refactor(zsh): shellcheck doesn't like me

zsh/.config/oh-my-zsh/custom/npm.zsh

@@ -11,4 +11,5 @@ PATH="$NPM_CONFIG_PREFIX/bin:$PATH"
 
 # Unset manpath so we can inherit from /etc/manpath via the `manpath` command
 unset MANPATH # delete if you already modified MANPATH elsewhere in your config
-export MANPATH="$NPM_CONFIG_PREFIX/share/man:$(manpath)"
+MANPATH="$NPM_CONFIG_PREFIX/share/man:$(manpath)"
+export MANPATH

zsh/.config/oh-my-zsh/custom/ruby.zsh

@@ -1,2 +1,3 @@
 # Add rubygem binary directory to $PATH
-export PATH="$PATH:$(ruby -e "puts Gem.user_dir")/bin"
+PATH="$PATH:$(ruby -e "puts Gem.user_dir")/bin"
+export PATH

zsh/.config/oh-my-zsh/custom/tmux.zsh

@@ -4,5 +4,5 @@ alias tmux='tmux -f ~/.config/tmux/tmux.conf'
 
 # Connect to remote tmux session via SSH
 ssh-tmux(){
-	ssh -t $@ "tmux attach || tmux new";
+	ssh -t "$@" "tmux attach || tmux new";
 }