CLOCK Cache

An implemenation of a CLOCK cache as first described in [A Paging Experiment with the Multics System] (http://multicians.org/paging-experiment.pdf).

Example

Below is a simple example of how to instantiate a CLOCK cache.

```rust,norun extern crate clockcache;

use clock_cache::ClockCache;

fn main() { let mut cache = ClockCache::new(2); cache.put("apple", "red"); cache.put("banana", "yellow");

    assert_eq!(*cache.get(&"apple").unwrap(), "red");
    assert_eq!(*cache.get(&"banana").unwrap(), "yellow");
    assert!(cache.get(&"pear").is_none());

    cache.put("pear", "green");

    assert_eq!(*cache.get(&"pear").unwrap(), "green");
    assert_eq!(*cache.get(&"banana").unwrap(), "yellow");
    assert!(cache.get(&"apple").is_none());

} ```