title: Laravel Migration to add foreign key not working
body: <p>I am back adding foreign keys to some tables but this one is not working.</p>
  
  <pre><code>Schema::table('users', function(Blueprint $table){
      $table-&gt;integer('account_type')-&gt;unsigned()-&gt;change();
      $table-&gt;foreign('account_type')
          -&gt;references('id')
          -&gt;on('account_types');
  });
  </code></pre>
  
  <p>It throws these 3 errors in terminal:</p>
  
  <pre><code>[Illuminate\Database\QueryException] SQLSTATE[HY000]: General error: 1215 Cannot add foreign key constraint (SQL: alter table `users` add constraint `users_account_type_foreign` foreign key (`account_type`) references `account_types` (`id`))
  
  
  [Doctrine\DBAL\Driver\PDOException]SQLSTATE[HY000]: General error: 1215 Cannot add foreign key constraint
  
  
  [PDOException] SQLSTATE[HY000]: General error: 1215 Cannot add foreign key constraint
  </code></pre>
  
  <p>Any idea what I need to do to fix this? I wan't to be able to click on the account_type field in my users table and be taken to the related account type in the account_types table whilst using SequelPro.</p>