speed improvments

- when using `Forklift::Patterns::Mysql.pipe`, we will build the destination table to a tmp location first and then rename it to the desired destination.  This will minimize the time that the destination table doesn't exist
- add a `Forklift::Patterns::Mysql.write_high_water_mark` method to stub data for all tables at a specific time
  - this is used to test your forklift ETL with partial data imports
- add `mysql.rename`
- update `mysql.write` to collect all writes into a single query rather than many queries per row.  This should speed up writes significantly.