fix installation script

install.zsh

@@ -2,28 +2,25 @@
 
 install_dotfile() {
   local dest="$1"
+  local contents="$2"
 
   if [[ -f "$dest" ]]; then
     mv -vi "$dest" "$dest.dmitmel-dotfiles-backup"
   fi
 
   mkdir -p "${dest:h}"
-  cat > "$dest"
+  echo "$contents" > "$dest"
 }
 
 # ZSH
 for zsh_file_name in zshrc; do
-  install_dotfile "$HOME/.$zsh_file_name" <<EOF
+  install_dotfile "$HOME/.$zsh_file_name" '
 #!/usr/bin/env zsh
 source "$PWD/zsh/$zsh_file_name"
-EOF
+'
 done
 unset zsh_file_name
 
 # Neovim
-install_dotfile ~/.config/nvim/init.vim <<EOF
-source $PWD/nvim/init.vim
-EOF
-install_dotfile ~/.config/nvim/ginit.vim <<EOF
-source $PWD/nvim/ginit.vim
-EOF
+install_dotfile ~/.config/nvim/init.vim 'source $PWD/nvim/init.vim'
+install_dotfile ~/.config/nvim/ginit.vim 'source $PWD/nvim/ginit.vim'