added unit test to EncoderDecoderTestGwt which demonstrates a problem with missing @class attribute in json when using an encoder of a concrete implementation instead of a super class. This leads to exceptions when decoding the created json to java object with jackson 2.3.2 on server side in a spring mvc controller
Merge pull request #212 from Koizumi85/polymorphic_encoder_problem

added unit test to EncoderDecoderTestGwt which demonstrates a problem wi...