Enable concatenation for dim-1 vectors
Enable concatenation for dim-1 vectors

sxjscience/mxnet,sxjscience/mxnet,sxjscience/mxnet,sxjscience/mxnet,sxjscience/mxnet,sxjscience/mxnet,sxjscience/mxnet,sxjscience/mxnet,sxjscience/mxnet