SINGA-292 Update CMakeLists.txt for compiling OpenBlas and Protobuf
SINGA-292 Update CMakeLists.txt for compiling OpenBlas and Protobuf

Update CMakeLists.txt to compile openblas using the 'optimized_for_deeplearning' branch
and set the PROTOBUF_PROTOC_EXECUTABLE path to build/bin/proto (which resulted in error when compiling on mac osx)

nusdbsystem/incubator-singa,nusdbsystem/incubator-singa,kaiping/incubator-singa,nudles/incubator-singa,kaiping/incubator-singa,nudles/incubator-singa,apache/incubator-singa,apache/incubator-singa,kaiping/incubator-singa,ijingo/incubator-singa,nudles/incubator-singa,ijingo/incubator-singa,nudles/incubator-singa,nudles/incubator-singa,ijingo/incubator-singa,nusdbsystem/incubator-singa,apache/incubator-singa,apache/incubator-singa,ijingo/incubator-singa,ijingo/incubator-singa,apache/incubator-singa,kaiping/incubator-singa,nusdbsystem/incubator-singa,kaiping/incubator-singa,nusdbsystem/incubator-singa