Webargs

*******************

* When parsing a nested ``Arg``, filter out extra arguments that are not part of the ``Arg's`` nested ``dict`` (:issue:`28`). Thanks Derrick Gilland for the suggestion.
* Fix bug in parsing ``Args`` with both type coercion and ``multiple=True`` (:issue:`30`). Thanks Steven Manuatu for reporting.
* Raise ``RequiredArgMissingError`` when a required argument is missing on a request.

******************

* Fix behavior of ``multiple=True`` when nesting Args (:issue:`29`). Thanks Derrick Gilland for reporting.

******************

* Pyramid support thanks to philtay.
* User-friendly error messages when ``Arg`` type conversion/validation fails. Thanks Andriy Yurchuk.
* Allow ``use`` argument to be a list of functions.
* Allow ``Args`` to be nested within each other, e.g. for nested dict validation. Thanks saritasa for the suggestion.
* *Backwards-incompatible*: Parser will only pass ``ValidationErrors`` to its error handler function, rather than catching all generic Exceptions.
* *Backwards-incompatible*: Rename ``Parser.TARGET_MAP`` to ``Parser.__target_map__``.
* Add a short-lived cache to the ``Parser`` class that can be used to store processed request data for reuse.
* Docs: Add example usage with Flask-RESTful.

******************

* Fix bug in ``TornadoParser`` that raised an error when request body is not a string (e.g when it is a ``Future``). Thanks Josh Carp.

******************

* Fix ``Parser.use_kwargs`` behavior when an ``Arg`` is allowed missing. The ``allow_missing`` attribute is ignored when ``use_kwargs`` is called.
* ``default`` may be a callable.
* Allow ``ValidationError`` to specify a HTTP status code for the error response.
* Improved error logging.
* Add ``'query'`` as a valid target name.
* Allow a list of validators to be passed to an ``Arg`` or ``Parser.parse``.
* A more useful ``__repr__`` for ``Arg``.
* Add examples and updated docs.

******************

* Add ``source`` parameter to ``Arg`` constructor. Allows renaming of keys in the parsed arguments dictionary. Thanks Josh Carp.
* ``FlaskParser's`` ``handle_error`` method attaches the string representation of validation errors on ``err.data['message']``. The raised exception is stored on ``err.data['exc']``.
* Additional keyword arguments passed to ``Arg`` are stored as metadata.