Attrs-to-sql

Fixed

- Use class name as table name instead of fixed name

Fixed

- Convert `attrs_to_sql.py` to `attrs_to_sql` package

Added

- Convert `attrs` class to `CREATE TABLE` command
- SQL types support: `int`, `timestamp`, `varchar` (with length), `float`, arrays
- SQL properties support: `PRIMARY KEY`, auto increment (via `serial`/`bigserial`), `NOT NULL`