title: Laravel migration self referencing foreign key issue
body: <p>Hi I have a problem to create a table using migration schema builder.
  The problem occure with table with self referencing foreign key.
  Here is the code which produce error:</p>
  
  <pre><code>        Schema::create('cb_category', function($table)
      {
          $table-&gt;integer('id')-&gt;primary()-&gt;unique()-&gt;unsigned();
          $table-&gt;integer('domain_id')-&gt;unsigned();
          $table-&gt;foreign('domain_id')-&gt;references('id')-&gt;on('cb_domain'); 
          $table-&gt;integer('parent_id')-&gt;nullable(); 
          $table-&gt;foreign('parent_id')-&gt;references('id')-&gt;on('cb_category')-&gt;onUpdate('cascade')-&gt;onDelete('cascade'); 
          $table-&gt;string('name');
          $table-&gt;integer('level');
      });
  </code></pre>
  
  <p>Here is the error:</p>
  
  <pre><code>  SQLSTATE[HY000]: General error: 1005 Can't create table 'eklik2.#sql-7d4_e' (errno: 150) (SQL: alter table `cb_cate
  </code></pre>
  
  <p>gory<code>add constraint cb_category_parent_id_foreign foreign key (</code>parent_id<code>) references</code>cb_category<code>(</code>id`) on del
    ete cascade on update cascade) (Bindings: array (
    ))</p>
  
  <p>[PDOException]
    SQLSTATE[HY000]: General error: 1005 Can't create table 'eklik2.#sql-7d4_e' (errno: 150)</p>
  
  <p>Any idea?</p>