Tried hand with session
Added urls necessary for user authentication
Added login view defination.
Added auth_view defination.
Added loggedin view defination.
Added invalid_login view defination.
Added logout view defination.
Added login template.
Added loggedin template.
Added invalid_login template.
Added logout template.
Added urls for registeration.
Added view for register_user
Added view for register_success
Added template for registeration.
Added template for register_success.
Article model is modified with default likes to zero
for for user registeration is added.
Modified for user registeration form.