Dyntastic

- Make commit limit configurable on `transaction()` context manager

- Fix issue with query returning no results when using a filter with sparse matches

- Add support for transaction writes using `transaction()` context manager
- No longer commit batch when an exception is raised during the batch context
manager `__exit__`

- Add support for `scan_index_forward` for specifying ascending (True) or
descending (False) traversal of the index.

- Add support for `__table_host__` for local testing

- Make mypy linting more strict