ALO
===
ALO means "At Least One".
ALO is simple data structure which contains at least one items.
ALO does not heap allocation until there is only one item.
```rust
// Initialize
let mut alo = ALO::with_item(42);
// Adding
alo.add(777);
alo.add(0);
// Removing
assert_eq!(Some(&42), alo.remove(0));
// Getting
assert_eq!(Some(&777), alo.get(0));
```