title: Foreign keys in Laravel 4 migrations issue
body: <p>I've just created a new Laravel 4 project and am finding strange things happening with the foreign key aspect of the schema builder. If I use the <code>-&gt;foreign()</code> method in any of my migrations I get thrown MySQL errors 150 and general error 1005. According to the documentation at laravel.com/docs the two scenario's at the bottom should work? Anyone know why they don't?</p>
  
  <p>The following does work:</p>
  
  <pre><code>    Schema::create('areas', function($table)
      {
          $table-&gt;engine ='InnoDB';
          $table-&gt;increments('id');
  
          $table-&gt;integer('region_id')-&gt;references('id')-&gt;on('regions');
  
          $table-&gt;string('name', 160);
          $table-&gt;timestamps();
      });
  </code></pre>
  
  <p>But these two do not work:</p>
  
  <pre><code>    Schema::create('areas', function($table)
      {
          $table-&gt;engine ='InnoDB';
          $table-&gt;increments('id');
  
          $table-&gt;foreign('region_id')-&gt;references('id')-&gt;on('regions');
  
          $table-&gt;string('name', 160);
          $table-&gt;timestamps();
      });
  
      Schema::create('areas', function($table)
      {
          $table-&gt;engine ='InnoDB';
          $table-&gt;increments('id');
  
          $table-&gt;integer('region_id');
          $table-&gt;foreign('region_id')-&gt;references('id')-&gt;on('regions');
  
          $table-&gt;string('name', 160);
          $table-&gt;timestamps();
      });
  </code></pre>