Not prune the bias about dynamic-network-surgery-caffe-reimplementation

[HolmesShuan]

To be clear:

1. Wx refers to without bias term rather than didn't prune the bias term.
2. We update the bias term during the fine-tuning process, thus the original bias should not be used.
3. DNS (Dynamic Network Surgery) set some small biases to zero, i.e. prune bias term. Strictly speaking, it is possible that all bias term are set to zero, in another word, Wx+0, which is equivalent to Wx. But we didn't prune bias, even if the value of some bias terms are very close to zero.