Add database cleaning with transaction

Right now you can clean the database with truncation: https://github.com/luckyframework/lucky_record/pull/137

The problem is it is super slow. Transactions are much faster, so transaction cleaning should be added.

It may be helpful to see how DatabaseCleaner did it: https://github.com/DatabaseCleaner/database_cleaner/blob/master/lib/database_cleaner/active_record/transaction.rb

Review the truncation approach referenced in lucky_record pull request 137 and compare it with DatabaseCleaner's active_record/transaction.rb example. Then locate Avram's database-cleaning entry point and add transaction cleaning alongside truncation; done means callers can use the transaction strategy for faster database cleaning.

Written by the indexing model from the issue text.