Normalize changelog and errata

0.5.0 Release, 7th July 2014

added support for comparing filtered objects; __pk__() object method no longer honored. See tests/test_mfs_diff.py for examples
MultiFieldSelector can now be traversed by indexing, and supports the in operator, with individual indices or FieldSelector objects as the member. See tests/test_selector.py for examples.
extraneous diff option now customizable via the DiffOptions sub-class API.

enhancement to diff to allow custom, per-field normalization of values before comparison
Some inconsistancies in JSON marshalling in were fixed

the return value from coerce functions is now checked against the type constraints (isa and check properties)
added capability of Property constructor to dynamically mix variants as needed; Almost everyone can now use plain Property(), ListProperty(), or a shorthand typed property declaration (like StringProperty()); other properties like Safe and Lazy will be automatically added as needed. Property types such as LazySafeJsonProperty are no longer needed and were savagely expunged from the codebase.
SafeProperty is now only a safe base class for Property sub-classes which have type constraints. Uses of make_property_type which did not add type constraints must be changed to Property type, or will raise exc.PropertyTypeMixNotFound
bug fix for pickling JsonRecord classes
filtering objects via MultiFieldSelector.get(obj) now works for JsonRecord classes.
The AttributeError raised when an attribute is not defined now includes the full name of the attribute (class + attribute)

much work on the diff mechanisms, results, and record identity
records which set a tuple for isa now work properly on stringification
semi-structured exceptions (normalize.exc)
the collections 'tuple protocol' (which models all collections as a sequence of (K, V) tuples) was reworked and made to work with more cases, such as iterators and generators.
Added DateProperty and DatetimeProperty