How to add multiple buttons to WordPress post editor with a single plugin?

I asked this question in the WordPress community and didn't get an answer, so I thought I'd reach out to this community as well.

I'm tweaking my WordPress installation and adding custom buttons to the visual editor using a custom plugin I wrote. For now, I've followed the tutorial and added a "code" button, but I also want to add a "quote" button that wraps the selected text in a <cite></cite>label. I'm sure I can duplicate the plugin and make smaller changes, but that seems clunky and inefficient and I'd rather add two buttons via the same plugin.

There is a related question about this problem here , but before, it's from a few years, and I'm using WordPress 3.9.1, using the newer version of TinyMCE (visual editor). So I'm not sure how much of this answer is relevant or how to apply it to TinyMCE 4.*.

Here is the PHP script I use to add the "code" button:

<?php

add_action( 'init', 'code_button' );

function code_button() {
    add_filter( "mce_external_plugins", "code_add_button" );
    add_filter( 'mce_buttons', 'code_register_button' );
}
function code_add_button( $plugin_array ) {
    $plugin_array['mycodebutton'] = $dir = plugins_url( 'shortcode.js', __FILE__ );
    return $plugin_array;
}
function code_register_button( $buttons ) {
    array_push( $buttons, 'codebutton' );
    return $buttons;

and the relevant JS file:

(function() {
    tinymce.create('tinymce.plugins.code', {
        init : function(ed, url) {

            ed.addButton('codebutton', {
                title : 'Code',
                cmd : 'codebutton',
                icon: 'icon dashicons-editor-code'
            });

            ed.addCommand('codebutton', function() {
                var selected_text = ed.selection.getContent();
                var return_text = '';
                return_text = '<code>' + selected_text + '</code>';
                ed.execCommand('mceInsertContent', 0, return_text);
            });
        },
        // ... Hidden code
    });
    // Register plugin
    tinymce.PluginManager.add( 'mycodebutton', tinymce.plugins.code );
})();

What changes do I need to make to these files to add another custom button?

Thanks!