Fix test

tests/decode_images.rs

@@ -170,7 +170,7 @@ fn test_decode_data() {
     let mut decoder = Decoder::new(file).unwrap();
     assert_eq!(decoder.colortype().unwrap(), ColorType::RGB(8));
     assert_eq!(decoder.dimensions().unwrap(), (100, 100));
-    if let DecodingResult::U8(img_res) = decoder.read_strip().unwrap() {
+    if let DecodingResult::U8(img_res) = decoder.read_image().unwrap() {
         assert_eq!(image_data, img_res);
     } else {
         panic!("Wrong data type");