半监督的GAN算法

ImprovedGAN

\( Loss = Loss_{supervised} \ + \lambda * Loss_{unsupervised} \)
第二项形式与原始的GAN模型类似。

参考： Improved Techniques for Training GANs
代码： https://github.com/Sleepychord/ImprovedGAN-pytorch/blob/master/ImprovedGAN.py