[ARITH] Add CombineInterval<Div> in IntSet (#48)
[ARITH] Add CombineInterval<Div> in IntSet (#48)

* [FIX] add CombineInterval<Div>

* fix error message and add comment about rounding

* fix comment

phisiart/tvm,Laurawly/tvm-1,dmlc/tvm,sxjscience/tvm,tqchen/tvm,phisiart/tvm,tqchen/tvm,sxjscience/tvm,Laurawly/tvm-1,tqchen/tvm,dmlc/tvm,phisiart/tvm,Laurawly/tvm-1,tqchen/tvm,Huyuwei/tvm,Laurawly/tvm-1,Laurawly/tvm-1,Laurawly/tvm-1,Huyuwei/tvm,sxjscience/tvm,Laurawly/tvm-1,sxjscience/tvm,Huyuwei/tvm,tqchen/tvm,sxjscience/tvm,sxjscience/tvm,dmlc/tvm,dmlc/tvm,Huyuwei/tvm,sxjscience/tvm,phisiart/tvm,Huyuwei/tvm,Huyuwei/tvm,sxjscience/tvm,Huyuwei/tvm,dmlc/tvm,tqchen/tvm,sxjscience/tvm,dmlc/tvm,phisiart/tvm,dmlc/tvm,tqchen/tvm,phisiart/tvm,Laurawly/tvm-1,tqchen/tvm,tqchen/tvm,Huyuwei/tvm,Laurawly/tvm-1,dmlc/tvm,Laurawly/tvm-1,dmlc/tvm,Huyuwei/tvm,tqchen/tvm,phisiart/tvm