stub for reference impl of rnnlm
stub for reference impl of rnnlm


Former-commit-id: fa690bf28e11eebd7cc4c63a1d02182509dda4f2
chunyang-wen/dynet,shuheik/dynet,danielhers/dynet,clab/cnn,xunzhang/dynet,chunyang-wen/dynet,xunzhang/dynet,clab/dynet,chunyang-wen/dynet,shuheik/dynet,clab/cnn,danielhers/dynet,danielhers/dynet,clab/dynet,shuheik/dynet,chunyang-wen/dynet,danielhers/dynet,shuheik/dynet,danielhers/dynet,danielhers/dynet,clab/dynet,clab/dynet,shuheik/dynet,clab/dynet,clab/dynet,xunzhang/dynet,danielhers/dynet,clab/cnn,shuheik/dynet,xunzhang/dynet,clab/dynet,shuheik/dynet