Sql-metadata

* 13 - `get_query_columns`: add support for INSERT queries
* 12 - handle empty query argument of `get_query_tokens `
* 19 - update dependencies
* 18 - `get_query_tables()` breaks on `INSERT INTO ... SELECT`
* 22 - move `normalize_sql` to `sql-metadata`

* 10 - Introduce `get_query_limit_and_offset()`

* 6 - Handle more complex SQL queries

* 4 - Handle more queries and add tests from [`query-digest`](https://github.com/macbre/query-digest/blob/master/tests/test_query_metadata.py)

* `sqlmetadata` extracted from [`index_digest`](https://github.com/macbre/index-digest/blob/master/indexdigest/query.py) - see #2