[Infer] More robust inference, support backward inference (#54)
[Infer] More robust inference, support backward inference (#54)


jermainewang/nnvm,piiswrong/nnvm,ZihengJiang/nnvm,piiswrong/nnvm,jermainewang/nnvm,imai-lm/nnvm,imai-lm/nnvm,piiswrong/nnvm,jermainewang/nnvm,imai-lm/nnvm,ZihengJiang/nnvm,ZihengJiang/nnvm