Boost 1.75 requires C++14
Compiling with C++11 using Boost 1.75 produces errors such as:
ring_type.hpp:127:18: error: no template named 'conditional_t' in namespace 'std'; did you mean 'conditional'?
std::conditional_t
Ideally, we switch to compiling with C++14 if Boost 1.75 detected and eventually switch over to C++14 by default.