Revert ".clean_with calls .clean instead of .clean_all as starndard behavior"

To be compatible with DatabaseCleaner usage

This reverts commit 05f59394cd4c4a299fa53729678b0f5b7ea7e7f9.
Use `ensure` to reset original values
Merge pull request #15 from deeeki/fix_clean_with

Fix `#clean_with` for compatibility