Brexit

For when you want to get rid of an object, you just need to do some administration first.

Usage example

This program will print "The UK has left" after 3 years.

```rust struct UnitedKingdom {}

impl Drop for UnitedKingdom {
    fn drop(&mut self) {
        println!("The UK has left")
    }
}

fn main() {
    let uk = UnitedKingdom{};
    brexit(uk);
    thread::sleep(Duration::from_secs(60*60*24*365*4));
}

```

I put all the blame @Dylan-DPC for encouraging me to make this ~~abomination~~ very useful crate.