[boost] [histogram] Objections against switch to C++14?

Dear reviewers of boost.histogram, thank you again for your reviews. I am currently working on the issues raised during the review and some of the requested features would be easier to implement when the library standard is raised from C++11 to C++14. This only affects the implementation side, not the user side. It would make my life easier and the implementation code more readable, because I can emulate `if constexpr` using in-place generic lambdas instead of out-of-place functors in the detail namespace. To make the library more user-friendly, I have to do more and more of these emulated `if constexpr`. Do you object against raising the requirement from C++11 to C++14 for the implementation of boost.histogram? Best regards, Hans