v0.6.0

[v0.6.0] - 2020-11-05

Added

• Field.sensitive property to mark a value as sensitive.
• Config.to_tree() now supports masking sensitive values (sensitive_mask parameter) and
  including virtual fields in the tree (virtual parameter).

Changed

• StringField now only accepts string values. Prior to this release, all input values were
  coerced to a string, via str(value). This was causing inconsistencies and non-intuitive
  behavior for fields that inherited from StringField.
• Refactor ListProxy to inherit from list.

Fixed

• ListField now handles empty or None values.