1. Rename variables by Google style.
2. Add more test cases.
3. Add more detail and meaningful comments.
4. Change type of "padding" to vector<int>

* init add

* add topk op

* someupdate

* fix style check

* add test py file

* update top k cuda kernel

* follow comments

* remove debug print

* fix casting error

* fix casting error

* fix casting error

* fix rename bug...

* fix travis

fix test_bi_grumemory.protostr, test_recursive_topology.protostr, util_layers.protostr and new test_sub_nested_seq_select_layer.protostr