使用composer自动加载自己的代码

I'm trying to build my own composer project and am trying to test out the code to ensure it works as I start building it. I've read through dozens of tutorials and stack overflow questions, and all seem to point to that I'm doing things right, though since it's not working, I imagine I'm not.

I have a file structure of:

index.php
composer.json
composer.lock
vendor/
src
    \Frankenstein
         \DB
            |FrankensteinDB.php

and have made the composer.json look as follows:

{
  "autoload": {
    "psr-4" : {"Frankenstein\\":"src/Frankenstein"}
  },
  "require": {
    "enrise/frisbee": "0.1.0"
  }
}

FrankensteinDB.php looks like:

<?php

namespace Frankenstein\DB;

use Frisbee\Exception\Flingable;

class FrankensteinDB extends Flingable
{   
    public function __construct($name)
    {
        parent::__construct($name, 1337);
    }

    public function run()
    {
    }

    public function next()
    {
    }
}

and of course lastly, the index.php is as follows:

<?php

require_once 'vendor/autoload.php';

use Frankenstein\DB\FrankensteinDB;

try {
    throw new FrankensteinDB('frankenstein');
} catch (Error $e){
    $e->getCode();
}

every time I run the code I get Class 'Frankenstein\DB\FrankensteinDB' not found and I just can't figure out why. I've tried about every combination of folders in the namespace, use, and composer psr-4 part and nothing seems to work. I also am running composer update after each change to be sure the autoload files get regenerated.