Fix some compiler warnings.

src/main.rs

@@ -11,7 +11,6 @@
 #![allow(clippy::needless_range_loop)]
 #![allow(clippy::excessive_precision)]
 
-#[macro_use]
 extern crate lazy_static;
 
 mod accel;

src/tracer.rs

@@ -12,8 +12,6 @@ use crate::{
     transform_stack::TransformStack,
 };
 
-use float4::Bool4;
-
 pub struct Tracer<'a> {
     ray_stack: RayStack,
     inner: TracerInner<'a>,