Refatorando método filtra_proposicao na classe Filtro_Proposicao()

Signed-off-by: Gabriel Augusto <gabriel.a.b@outlook.com>
Signed-off-by: Tallys Martins <tallysmartins@gmail.com>
Signed-off-by: Winstein Martins <sriwinstein@gmail.com>
Issue #137
Escrevendo testes para os metodos da  classe Filtro_Proposicao()

Signed-off-by: Gabriel Augusto <gabriel.a.b@outlook.com>
Signed-off-by: Tallys Martins <tallysmartins@gmail.com>
Signed-off-by: Winstein Martins <sriwinstein@gmail.com>