This change permits to use up-to-date compilers, clang-tidy and
clang-format
It also refactor the tidy/format step to drop the binary selection from
scripts and perform it directly in travis
* Promote performance-type-promotion-in-math-fn as a coding error
* Promote performance-faster-string-find too (which is not problematic currently)
* Same for performance-implicit-cast-in-loop
* Fix remaining tidy points
* Implement new travis clang-tidy build step
* This step enable some rules and enforce one rule as error
* This permits to have some C++ quality rules based on clang & clang contributor guidelines
* Fix clang-tidy reported problems on push_back -> emplace_back
