0.2.0 - `field` improvements

• New type argument in field to declare the type of a field. If provided, the descriptor will not be replaced with a native field, and the type will be checked on every value modification. A TypeError will be raised if type does not comply. Type hints are correctly defined so that IDEs can pick them. Fixes #3

• New use_descriptor argument in field to force use a descriptor instead of a native field.

See documentation page for details.