`Shape::get_bound` assumes 0,0 is inside the bounding box

It uses

```rust
let mut bound = Bound::default();
```

as its initial bounding box, which contains all zeroes. If the shape does not contain the origin, this results in an incorrect box. The initial box should probably be something like

```rust
let mut bound = Bound {
    left: f64::INFINITY,
    bottom: f64::INFINITY,
    right: -f64::INFINITY,
    top: -f64::INFINITY,
};
```