Check-in broken & partial try_read_u32 function

I'm saving this to the repo so I can possibly come back and fix it up
correctly.

A major API change is going to be attempted. The iterator-based stream
processing has proven to be fiddly and annoying, so I'm going to switch
to a processing the complete image.

src/decoder.rs

@@ -19,8 +19,13 @@ pub fn try_read_magic<I: Iterator<Item=u8>>(bytes: &mut I) -> Result<(), DecodeE
 
 fn try_read_u32<I: Iterator<Item=u8>>(bytes: &mut I) -> Result<u32, DecodeError> {
     let mut res: u32 = 0;
-    
-    Ok(res) 
+    let i = bytes.take(4)
+        .enumerate()
+        .reduce(|acc, (idx, val)| {
+            (0, 0)
+        });
+
+    Ok(res)
 }
 
 mod codec_utils {