Mention C++14 in the README (#26670)
Summary:
Technically, we don't need a C++14 compiler yet, but we will soon stop support for GCC 4. Requiring a "C++14" compiler excludes GCC 4, so it is a defensive statement. Some time later, we will actually require a C++14 compiler.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/26670
Differential Revision: D17907257
Pulled By: smessmer
fbshipit-source-id: 5363d714f8d93597db008135f681b2e14d052fa0
