Minor fixups and doc updates.

tests/sha256.rs

@@ -63,7 +63,6 @@ fn test_golden_tests() -> Result<()> {
     let mut s: [u8; 64] = [0; 64];
 
     while i < golden_tests.len() {
-        eprintln!("golden test: {:}", i);
         h.update(golden_tests[i].input)?;
         h.finalize(&mut d)?;
         hexstr(&d, &mut s);