Remove TODO: make tag constants u5s

Using the u5 type for tag constants would clean up the code at
some places, but to achieve this a workaround for constructing
these constants would be necessary (since rust has no constexpr
functions yet).

All workarounds I see aren't worth it (unsafe or lazy_static).

Author: sgeisler

src/ser.rs

@@ -266,7 +266,6 @@ impl ToBase32<Vec<u5>> for TaggedField {
 		assert!(data.len() < 1024, "Every tagged field data can be at most 1023 bytes long.");
 
 		let mut sized_data = Vec::<u5>::with_capacity(data.len() + 3);
-		// TODO: think about saving tag constants as u5c
 		sized_data.push(u5::try_from_u8(tag).expect("Tags should be <32."));
 		sized_data.extend_from_slice(
 			&try_stretch(