CMake: Update minimum required CMake version because the LLVM integration requires tar.xz decompression support which was added in 3.1
CMake: Update minimum required CMake version because
the LLVM integration requires tar.xz decompression support
which was added in 3.1

NervanaSystems/ngraph,NervanaSystems/ngraph,NervanaSystems/ngraph,NervanaSystems/ngraph