Use built-in constant instead of a magic number (#18)

In job-security providing functions, it is critically important that
they be fully in line with best coding practices. Hence, instead of
using a well-known(ish!) hardcoded power of two, use u8::MAX to truncate
the u32 into a u8.

src/lib.rs

@@ -83,7 +83,7 @@ pub fn give_up<T: 'static>() -> Box<T> {
 	let mut rng = oorandom::Rand32::new(seed());
 
 	for _ in 0..size {
-		v.push((rng.rand_u32() % 256) as u8);
+		v.push((rng.rand_u32() & u32::from(u8::MAX)) as u8);
 	}
 
 	crate::transmute(v.into_boxed_slice())