Confu

Fixed
- some attribute validators still have issues with a None default (16)
- For string attributes a blank default value should infer blank=True (15)

Fixed
- IPAddress field validation issue with blank=True (13)
- Allow None as a default value (14)
- Auto set attribute name if not specified (12)
- added `valid` property to Config that will be true if config was validated without
- code cleanup
- test coverage to 91%
- updated outdated requirements to prepare for 1.0.0 release

Added
- `blank` argument for `Str` attribute - specifies whether value can be blank or not, defaults to `False`
Fixed
- proxy schema needs to be able to apply defaults (10)
- issue where list validation would sometimes lead to duplicate items added to the list
Changed
- `Directory` attribute will forfeit validation if `blank` is `True` and value is `""`

Fixed
- recursive directory creation for Directory Attribute if `create` is specified