Webargs

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

* Fix bug in ``TornadoParser's`` ``handle_error`` method. Thanks Josh Carp.
* Add ``error`` parameter to ``Parser`` constructor that allows a custom error message to be used if schema-level validation fails.
* Fix bug that raised a ``UnicodeEncodeError`` on Python 2 when an Arg's validator function received non-ASCII input.

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

* Fix regression with parsing an ``Arg`` with both ``default`` and ``target`` set (see issue 11).

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

* Add ``validate`` parameter to ``Parser.parse`` and ``Parser.use_args``. Allows validation of the full parsed output.
* If ``allow_missing`` is ``True`` on an ``Arg`` for which ``None`` is explicitly passed, the value will still be present in the parsed arguments dictionary.
* *Backwards-incompatible*: ``Parser's`` ``parse_*`` methods return ``webargs.core.Missing`` if the value cannot be found on the request. NOTE: ``webargs.core.Missing`` will *not* show up in the final output of ``Parser.parse``.
* Fix bug with parsing empty request bodies with ``TornadoParser``.

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

* Fix behavior of ``Arg's`` ``allow_missing`` parameter when ``multiple=True``.
* Fix bug in tornadoparser that caused parsing JSON arguments to fail.

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

* Fix JSON parsing in Flask parser when Content-Type header contains more than just `application/json`. Thanks Samir Uppaluru for reporting.
* *Backwards-incompatible*: The ``use`` parameter to ``Arg`` is called before type conversion occurs. Thanks Eric Wang for the suggestion.
* Tested on Tornado>=4.0.

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

* Custom target handlers can be defined using the ``Parser.target_handler`` decorator.
* Error handler can be specified using the ``Parser.error_handler`` decorator.
* ``Args`` can define their request target by passing in a ``target`` argument.
* *Backwards-incompatible*: ``DEFAULT_TARGETS`` is now a class member of ``Parser``. This allows subclasses to override it.