add op registry

fix #220 add prior_box_op and testfile

update code style to Google

switch code style tool to cpplint

add some gitignore option & modify to 2 spaces indent & format code & rm build folder

fix #210 add pool& pool test fix #211 add executor for testing op

fix #208 program optimize generate graph

fix #206 add batchnorm and batchnorm_test

fix #204 add lrn_op and lrn_op_test

fix #202 add concat and concat_test

fix #200 change op test file (add,mul)

Add clang-tidy and clang-format hook