vectorize attention weight loop
vectorize attention weight loop


Former-commit-id: c4ca3a4f4bf51d72cb9adf1c76eab0ee83fab1ee
danielhers/dynet,clab/dynet,shuheik/dynet,clab/dynet,shuheik/dynet,xunzhang/dynet,clab/cnn,chunyang-wen/dynet,xunzhang/dynet,xunzhang/dynet,clab/dynet,chunyang-wen/dynet,danielhers/dynet,clab/dynet,shuheik/dynet,clab/cnn,clab/dynet,danielhers/dynet,danielhers/dynet,danielhers/dynet,danielhers/dynet,shuheik/dynet,shuheik/dynet,clab/dynet,chunyang-wen/dynet,clab/dynet,shuheik/dynet,clab/cnn,shuheik/dynet,xunzhang/dynet,danielhers/dynet,chunyang-wen/dynet