* mem opt

* test=develop

* test=develop

* test=develop

* test=develop

* test=develop

* test=develop

* test=develop

* refine code  test=develop

* refine code  test=develop

* refine code  test=develop

* refine code  test=develop

* refine with cub test=develop

* fix mkldnn test && remove comments && test=develop

* polish code && test=develop

* add only_forward test && test=develop

* Init slim.

* Remove distillation demo.

* Fix import errors.
test=develop

* Fix some issues.
test=develop

* Fix configs.
test=develop

* Modify API.spec.
test=develop

* Fix format.
test=develop

* Fix format.
test=develop

* Add some comments.

* fix utils config, test=develop

* reweite tools in lookup table utils, test=develop

* merge develop, test=develop

* add copy in setup, test=develop

* update api spec, test=develop

* add doc, test=develop

* prettifying doc, test=develop

* Update API.spec

update api.spec, test=develop

* Update lookup_table_utils.py

test=develop

* Update lookup_table_utils.py

test=develop

* merge develop, test=develop

* merge develop, test=develop

* init fix, test=develop

* fix in downloads, test=develop

* fix in setup.in, test=develop

*  fix mkdir conflict

*  fix load/save lookup tables

 test=develop

* add lookup_table_utils

* fix load optimize vars on pserver

* delete lookup table utils

* fix save and load lookup tables

* fix load optimizer var

* fix load optimizer var, test=develop

* fix python 3 style, test=develop

* move lookup_table_utils to contrib utils

* add hdfs utils

* add hdfs utils

* test=develop

* update hdfs utils and add demo

* fix multi_download return local files

* test=develop

* add sync multi upload, test=develop

* add recordio support

* disable the openblas multi-thread on windows since no support
adjust the python script

* code style

* code style
test=develop

* add create_recordio_file_reader back

* fix code style
test=develop

* fix the gtest.cmake on windows

* fix cc_test on windows

* fix the win build
test=develop

* remove fused compile support on windows
test=develop

* add the jit support
test=develop

* add the jit support, test=develop

* add the jit support, test=develop

* add the jit back
fix compile error on windows

* rollback test=develop

* test case fix

* disable DSO by default on windows

* exclude warpctc_op on windows

* exclude the dynload_warpctc out on windows
test=develop

* fix the scripts error
test=develop

* disable avx on windows by default
test=develop

* re-organize the cmake file

* disable mkl on windows by default

* add warp_ctc back

* fix the dependency

* fix the dependency

* fix the build issue on windows

* remove unsupported flag on windows

* code style

* code style
test=develop

* fix issue

* add profiler, parallel_executor back

* clean up the pre-definitions on windows

* fix build issue

* test=develop

adjust the python script

1. Non utf-8 characters within comments of OPs may lead to protobuf fail to parse_from_string
2. comment out some ops which not supported on windows
3. cuda libs may not be correctly linked to target on windows

test=develop