fix brnn serialization (#33)
fix brnn serialization (#33)

BiEncoder's submodules are plain Encoder objects that contain clones
and preallocated Tensors. We have to save the serialized form of
these submodules.

da03/OpenNMT,jungikim/OpenNMT,jsenellart/OpenNMT,da03/OpenNMT,jsenellart-systran/OpenNMT,jungikim/OpenNMT,OpenNMT/OpenNMT,OpenNMT/OpenNMT,jsenellart-systran/OpenNMT,monsieurzhang/OpenNMT,monsieurzhang/OpenNMT,jsenellart/OpenNMT,jsenellart-systran/OpenNMT,srush/OpenNMT,jungikim/OpenNMT,da03/OpenNMT,OpenNMT/OpenNMT,jsenellart/OpenNMT,cservan/OpenNMT_scores_0.2.0,monsieurzhang/OpenNMT