Sqlalchemy-cratedb

- Added support for `Insert` from select
- Support `get_columns` and `get_pk_constraint`

- BREAKING: Dropped support for SQLAlchemy < 1.0.0
- Fix: The dialect didn't work properly with alpha and beta
versions of sqlalchemy due to a wrong version check
(e.g.: sandman2 depends on 1.1.0b3)
- Added support for native Arrays
- Fix: `sa.inspect(engine).get_table_names` failed due
to an attribute error

- Added compatibility for SQLAlchemy version 1.1

- Fix: Updates in nested `OBJECT` columns have been ignored

- Fix: `Date` column type is now correctly created as `TIMESTAMP` column
when creating the table

- Added support for serialization of Decimals