Reverted read_strip and read_tile to previous call signature

Added comments to ChunkInfo

tests/decode_images.rs

@@ -276,7 +276,7 @@ fn test_tiled_incremental() {
 
     for tile in 0..tiles {
         match decoder.read_tile().unwrap() {
-            (DecodingResult::U8(res), _chunk_info) => {
+            DecodingResult::U8(res) => {
                 let sum: u64 = res.into_iter().map(<u64>::from).sum();
                 assert_eq!(sum, sums[tile as usize]);
             }

tests/encode_images.rs

@@ -513,7 +513,7 @@ fn test_rows_per_strip() {
         for i in 0..50 {
             let img2 = [i; 2 * 100];
             match decoder.read_strip().unwrap() {
-                (DecodingResult::U8(data), _chunk_info) => assert_eq!(&img2[..], &data[..]),
+                DecodingResult::U8(data) => assert_eq!(&img2[..], &data[..]),
                 other => panic!("Incorrect strip type {:?}", other),
             }
         }