Ray Tracing in One Weekend, but in rust.

A ray tracer written in rust, using Peter Shirley book as guide: https://raytracing.github.io/books/RayTracingInOneWeekend.html

Notes and TODO's:

1. Why do we need this type of MaterialClone trait? And also why cant we call clone on geometry.rs and can only call clone_box?

pub trait  MaterialClone {
    fn clone_box(&self) -> Box<dyn Material>;
}

impl<T> MaterialClone for T
where
    T: 'static + Material + Clone,
{
    fn clone_box(&self) -> Box<dyn Material> {
        Box::new(self.clone())
    }
}

impl Clone for Box<dyn Material> {
    fn clone(&self) -> Box<dyn Material> {
        self.clone_box()
    }
}

2. Fix bug on thread tilling logic.