CMake minimum required 3.0 -> 3.1

[newEntera]

minimum required 3.0 is a bit contradiction to my experience. it should be 3.1 because CMake 3.1 introduced the CMAKE_CXX_STANDARD. Cmake 3.1 compiles fine, but CMake 3.0 does not have the CMAKE_CXX_STANDARD and then it does not use cxx11 then you hit error: expected template-name before ‘<’ token error enabled_shared_from_this