Added unit test for new signature. this refs #294

    # case_1: load data from given directory

    rst = load_data(ct_dir="/tmp", ob_dir="/tmp", dc_dir="/tmp")

    np.testing.assert_almost_equal(np.array(rst).flatten(), np.arange(1, 5, dtype=float))

    # case_2: load ct from directory, ob and dc from files

    rst = load_data(ct_dir="/tmp", ob_files=["3", "4"], dc_files=["5", "6"])

    np.testing.assert_almost_equal(np.array(rst).flatten(), np.arange(1, 5, dtype=float))

def test_forgiving_reader():