message: Fixed incorrect version number in README
  clang-900.0.39.2 is from LLVM 9.0.0, not 8.1.0
diff: @@ -834,7 +834,7 @@ The following compilers are currently used in continuous integration at [Travis]
  | Clang Xcode 8.3 | Darwin Kernel Version 16.5.0 (macOS 10.12.4) | Apple LLVM version 8.1.0 (clang-802.0.38) |
  | Clang Xcode 9.0 | Darwin Kernel Version 16.7.0 (macOS 10.12.6) | Apple LLVM version 9.0.0 (clang-900.0.37) |
  | Clang Xcode 9.1 | Darwin Kernel Version 16.7.0 (macOS 10.12.6) | Apple LLVM version 9.0.0 (clang-900.0.38) |
  -| Clang Xcode 9.2 | Darwin Kernel Version 16.7.0 (macOS 10.12.6) | Apple LLVM version 8.1.0 (clang-900.0.39.2) |
  +| Clang Xcode 9.2 | Darwin Kernel Version 16.7.0 (macOS 10.12.6) | Apple LLVM version 9.0.0 (clang-900.0.39.2) |
  | Visual Studio 14 2015 | Windows Server 2012 R2 (x64) | Microsoft (R) Build Engine version 14.0.25420.1, MSVC 19.0.24215.1 |
  | Visual Studio 2017 | Windows Server 2016 | Microsoft (R) Build Engine version 15.5.180.51428, MSVC 19.12.25830.2 |
  