Add some tests to make sure the code is valid

Dependencies

• [2] YA6A53B5 Init

Change contents

• replacement in src/main.rs at line 19
  [2.5890]→[2.5890:5923](∅→∅)
  − p.lookup(i * i);
  [2.5890]

  [2.5923]
  + let v = p.lookup(i * i);

  + assert_eq!(v, Some(i * i * i));
• replacement in src/main.rs at line 25
  [2.6005]→[2.6005:6057](∅→∅)
  − println!("{:?} {:?}", total_put, total_lookup);
  [2.6005]

  [2.6057]
  + println!("linked-list: {:?} {:?}", total_put, total_lookup);
• replacement in src/main.rs at line 42
  [2.6602]→[2.6602:6639](∅→∅)
  − p.lookup_ord(i * i);
  [2.6602]

  [2.6639]
  + let v = p.lookup_ord(i * i);

  + assert_eq!(v, Some(i * i * i));
• replacement in src/main.rs at line 48
  [2.6721]→[2.6721:6773](∅→∅)
  − println!("{:?} {:?}", total_put, total_lookup);
  [2.6721]

  [2.6773]
  + println!("ordered-vec: {:?} {:?}", total_put, total_lookup);
• replacement in src/main.rs at line 73
  [2.7611]→[2.7611:7663](∅→∅)
  − println!("{:?} {:?}", total_put, total_lookup);
  [2.7611]

  [2.7663]
  + println!("skip-list: {:?} {:?}", total_put, total_lookup);