upgrade required minimum cmake version
Created by: cocodark
we found compile error on ubuntu with cmake 3.5.1, so current minimum version 3.0 is not compatible.refer https://github.com/PaddlePaddle/paddle-mobile/issues/559
Created by: cocodark
we found compile error on ubuntu with cmake 3.5.1, so current minimum version 3.0 is not compatible.refer https://github.com/PaddlePaddle/paddle-mobile/issues/559