Version 0.2.0

This is a minor version change because of relatively significant
changes to array handling.

Prior to now, arrays objects were handled a little weirdly in that
they were stored as native python lists with an associated validator
object. This resulted in all sorts of unexpected behavior, with
nested arrays being returned without their validators under certain
circumstances.

This resolves the issue by converting all arrays to first-class object
wrappers (and renaming the wrapper to ArrayWrapper instead of
ArrayValidator).