message: Mention the preferred C++ standard.
diff: @@ -148,6 +148,8 @@ will allow us to reach you directly with project announcements.
  - New features should be added only if they are necessary or generally useful.
  - Introduction of language constructions not currently used in MFEM should be
  justified and generally avoided (so we can build on cutting-edge systems).
  + - We prefer basic C++ and the C++03 standard, to keep the code readable by
  + a large audience and to make sure it compiles anywhere.
  - *Keep the code general and reasonably efficient*
  - Main goal is fast prototyping for research.
  