fix py3 compatible printing in the visualizer
fix py3 compatible printing in the visualizer


Former-commit-id: 51b74c40a5cc6557349466ecc4f32c0c097dc04d
xunzhang/dynet,danielhers/dynet,chunyang-wen/dynet,clab/dynet,clab/dynet,shuheik/dynet,xunzhang/dynet,clab/dynet,danielhers/dynet,clab/dynet,shuheik/dynet,danielhers/dynet,chunyang-wen/dynet,shuheik/dynet,clab/dynet,shuheik/dynet,chunyang-wen/dynet,xunzhang/dynet,clab/cnn,danielhers/dynet,xunzhang/dynet,danielhers/dynet,shuheik/dynet,shuheik/dynet,clab/cnn,chunyang-wen/dynet,danielhers/dynet,clab/dynet,danielhers/dynet,clab/dynet,shuheik/dynet,clab/cnn