neovim: uses vimUtils to make it configurable like vim_configurable is

- vimAlias argument , when true, will create a @out/bin/vim symlink
- configure argument, which will configure neovim the same way as it does
  vim_configurable. eg.: ~/.nixpkgs/config.nix

    {

      packageOverrides = pkgs : with pkgs; rec {
        vimg = neovim.override {
          vimAlias = true;
          configure = {
            customRC = ''
              set spell
            '';
            vam.pluginDictionaries = [
              { names = [ "youcompleteme" "ctrlp"]; }
            ];
          };
        };
      };

     }

Enjoy!