Fix compatibility issues with torch==1.1.0

[jianchao-li]

• [x] torch.utils.serialization has been removed. torchfile.load should be used instead.
• [x] Fix the following error according to suggestions by @alvinwan

RuntimeError: Error(s) in loading state_dict for Net:
    Unexpected running stats buffer(s) "model1.1.running_mean" and "model1.1.running_var" for InstanceNorm2d with track_running_stats=False. If state_dict is a checkpoint saved before 0.4.0, this may be expected because InstanceNorm2d does not track running stats by default since 0.4.0. Please remove these keys from state_dict. If the running stats are actually needed, instead set track_running_stats=True in InstanceNorm2d to enable them. See the documentation of InstanceNorm2d for details.

[GreenTeaHua]

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