Add a nice simple WSGI server for real HTTP tests
Add new methods to browser and tests.

This is the first atempt to add some extra methods to the browser and
dom element.

But after adding them I found something I don't like: the class
hierarchy. It has two problems.
- The first I just created it adding some methods in a base class and
  overrding them changing the signature in a child class.
- The second is that the base class uses a child class :? And here
  starts my next refactor.