Add Readme file
ActivityDAO

addActivity method added to ActivityDAO.
Update README
Update ActivityDAO.class.php

public function removeAcitivty($id) implemented. 
public function findAll() added. 
public function findAll() implemented.
return $this added

returning $this was missing in the try statement of findAllActivity() method.
ActivityDAO

Syntax error changed from if to foreach
test.php

page dedicated to test the DAOs + classes
ActivityDAO.php

function updateActivity added. (not completly implemented yet)
Global commit

All classes including the Database one are tested and work fine.
UsersDAO.class.php works fine, but more verifications needed.
ActivityDAO.class.php isn't yet tested.
Merge PHP With CSS