Revert "Change value to monitor in callbacks: val_loss -> val_cider"
Revert "Change value to monitor in callbacks: val_loss -> val_cider"

Because val_cider is not every epoch

This reverts commit cc4dd7f118c5e031388c0dbe46fbce4582f8e9e2.

danieljl/keras-image-captioning,danieljl/keras-image-captioning