LowMap

A convenient wrapper around a Vec<Option<T>>. It abstracts the optional presence of an element as being a non contiguous vector.

```rust let mut map = LowMap::new(); map.insert(0, "hey"); map.insert(2, "hoy"); map.insert(3, "foo"); map.insert(2, "bar");

asserteq!(map.get(0), Some(&"hey")); asserteq!(map.get(1), None); asserteq!(map.get(2), Some(&"bar")); asserteq!(map.get(3), Some(&"foo"));

map[2] = "hoho"; assert_eq!(map.get(2), Some(&"hoho")); ```