message: bump requirements in docs
diff: @@ -84,8 +84,8 @@ experiments and usage attempts are very encouraging.
  This repository contains a C++ library for building, manipulating and
  serializing VPack data. It is the *reference implementation for the
  -VelocyPack format*. The library is written in good old C++11 so it
  -should compile on most systems.
  +VelocyPack format*. The library is written in C++17 so it should compile
  +on many up-to-date systems.
  Specification
  @@ -108,7 +108,7 @@ Building the VPack library
  The VPack library can be built on Linux, MacOS and Windows. It will likely
  compile and work on other platforms for which a recent version of *cmake* and
  -a working C++11-enabled compiler are available.
  +a working C++17-enabled compiler are available.
  See the file [Install.md](Install.md) for compilation and installation
  instructions.
  