build caffe2 wheel package for python3 on windows

build_caffe2_for_python3_win

Build Caffe2 CPU version on windows platform with python3:
	1. Pip install prerequisites packages
	2. Download protobuffer3.1(.exe file) from website
	3. Add code in caffe2\caffe2\python\pybind_state.cc to build correctly for Python3.5:
	
	#if PY_MAJOR_VERSION >= 3
	#ifndef PyString_AsString
	#define PyString_AsString PyUnicode_AsUTF8
	#endif
	#ifndef PyString_Check
	#define PyString_Check PyUnicode_Check
	#endif
	#endif 
	4. Build lmdb package:
	Can NOT use Nuget package. 
	Need to download lmdb files (lmdb.h mdb.c midl.h midl.c) from github, and build as static library(/MT).
	
	5. Make "build_XX" directory under caffe2 directory
	6. In" build_XX" directory, run:
		a. Set LMDB_DIR (the lmdb library is built to static library(/MT) [not dynamic library]):
		<directory of LMDB library>
		set LMDB_DIR=D:\src\packages\lmdb.v140.0.9.17\Release
		
		b. Run Cmake:
			cmake ../ -G"Visual Studio 14 2015 Win64" -DCMAKE_VERBOSE_MAKEFILE=1 -DBUILD_SHARED_LIBS=OFF -DBUILD_TEST=OFF -DCMAKE_BUILD_TYPE=Release -DUSE_CUDA=OFF -DPROTOBUF_PROTOC_EXECUTABLE=D:\src\protoc-3.1.0-win32\bin\protoc.exe -DCMAKE_CXX_FLAGS=/MP || exit /b
      cmake --build . --config Release || exit /b
      
      [NOTE]
      1) If you want to use cuda, you must build with -G"Visual Studio 14 2015 Win64"
      2) If you just use CPU only, you can build with -G"Visual Studio 15 2017 Win64"
      
	7. Write setup.py, MANIFEST.in, README.rst [optional: requirements.txt, test-requirements.txt]
	8. Create wheel, run:
		python setup.py bdist_wheel --universal
		
	9. If you want to specified python version: add this when run cmake command (the example is run in LINUX):
		-DPYTHON_EXECUTABLE=/usr/bin/python3.5