Exercise: Generic min

In this short exercise, you will implement a generic min function that determines the minimum of two values, using the Ord trait.

1. ```
   use std::cmp::Ordering;
   ```

3. ```
   // TODO: implement the `min` function used in `main`.
   ```

5. ```
   fn main() {
   ```
6. ```
       assert_eq!(min(0, 10), 0);
   ```
7. ```
       assert_eq!(min(500, 123), 123);
   ```

9. ```
       assert_eq!(min('a', 'z'), 'a');
   ```
10. ```
        assert_eq!(min('7', '1'), '1');
    ```

12. ```
        assert_eq!(min("hello", "goodbye"), "goodbye");
    ```
13. ```
        assert_eq!(min("bat", "armadillo"), "armadillo");
    ```
14. ```
    }
    ```

This slide and its sub-slides should take about 10 minutes.