Need to run prediction before DeepExplain when a model is loaded from file

[marcoancona]

Another problem, if I load a model from file, I must predict one time before generating saliency maps ,otherwise it will raise an exception:
"tensorflow.python.framework.errors_impl.InternalError: Blas SGEMM launch failed : m=21609, n=128, k=64

But if I use this model to predict one time, after that DeepExplain run well.

Originally posted by @linchundan88 in #36 (comment)