Add staging test case

Wrong base class before.

Patch would be nice.

Allow for $this->stagingUrl to be set in test itself instead of variable.

I gotta say, pretty slick.

class DrupalRedesignTestCase extends DrupalStageTestCase {

  public static function getInfo() {
    return array(
      'name' => 'AAA',
      'description' => '...',
      'group' => 'AAA',
    );
  }

  protected function setUp() {
    $this->stagingUrl = 'http://staging6.drupal.org';
    $this->httpauth_credentials = 'drupal:drupal';

    parent::setUp();
  }

  protected function testFoo() {
    $this->drupalGet('about');
    $this->assertText('Documentation');
  }
}

Actually it has already been committed in 7.x-2.x so lets just move it there and more it fixed. We will need a general issue it merge 7.x-2.x with 8.x