cascade [before/after]Each()

[tj]

ex:

var app;

describe('config', function(){
  beforeEach(function(){
    app = express();
  })

  describe('.set()', function(){
    it('should set a value', function(){
      app.set('foo', 'bar').should.equal(app);
    })
  })

  describe('.get()', function(){
    it('should get a value', function(){
      //...
    })
  })
})