Test use_kwargs on methodview
Args can define which target to parse from via the Arg.target attribute
Update docs and changelog
Test against py34 on travis
Make DEFAULT_TARGETS a class member
Fix targets param of use_args
Add versions to requirements
Bump dev version
Add target_handler decorator for registering custom parsing handlers
Update docs
Error handlers can be defined using the error_handler decorator
Simplify target_handler decorator

Also, fix indentation
Make _get_value protected instead of private
Bump version