Update tests.rs

0.9.0

- Make file-backed memmap `SkipMap` and `SkipSet` still can be reopened even the last time the program was aborted.
- Remove checksum validation. Users should take care of data integrity by themselves.
- Support `Clone` directly; no need to use the `Arc` wrapper anymore.
- Add `OpenOptions` and `MmapOptions` to support better controls on file memmap backed `SkipMap` and `SkipSet`.

Support `SkipMap::insert_with`

- Make `SkipMap::insert` and `SkipSet::insert` return the current value if the key and trailer already exist.
- Add the `SkipMap::insert_with` method to support inserting an occupied key first, then write the value in the closure semantic.

Optimize iterators and `Arena::alloc` logic

* Add remaining API

* Optimize `Arena::alloc` logic

* Implement `Iterator` trait for `MapIterator` and `SetIterator`

Update README.md

fix all miri errors

Update README.md