title: Make column not nullable in a Laravel 5 migration
body: <p>I have found this question very similar to mine <a href="https://stackoverflow.com/questions/14013832/make-column-not-nullable-in-a-laravel-migration">Make column not nullable in a Laravel migration</a> though it is almost 3 years old and it surely does not belong to Laravel 5</p>
  
  <p>My problem is that I have a migration which in the <code>up</code> function it modifies a column to make it nullable. 
  Now, in the <code>down</code> function I want to make it not nullable again.</p>
  
  <pre><code>/**
   * Run the migrations.
   *
   * @return void
   */
  public function up()
  {
      Schema::table('mytable', function(Blueprint $table) {
          $table-&gt;string('mycolumn')-&gt;nullable()-&gt;change();
      });
  }
  
  /**
   * Reverse the migrations.
   *
   * @return void
   */
  public function down()
  {
      Schema::table('mytable', function(Blueprint $table) {
      /* THIS IS WHAT I WOULD EXPECT TO DO
      THOUGH OF COURSE THE FUNCTION notNullable DOES NOT WORK */
          $table-&gt;string('mycolumn')-&gt;notNullable()-&gt;change(); 
      });
  }
  </code></pre>
  
  <p>I could achieve that using raw SQL, but I would like to do it using Laravel methods if it is possible... but I couldn't find it, probably it hasn't been implemented it in the version 5 either.</p>