message: Fix instructions for MAC
diff: @@ -43,7 +43,7 @@ For Ginkgo core library:
  * C++11 compliant compiler, one of:
  * _gcc 4.8.1+_ (__TODO__: verify)
  * _clang 3.3+_ (__TODO__: verify)
  - * _Apple LLVM 9.0+_
  + * _Apple LLVM 8.0+_ (__TODO__: verify)
  The Ginkgo GPU module has the following __additional__ requirements:
  @@ -51,8 +51,7 @@ The Ginkgo GPU module has the following __additional__ requirements:
  * _CUDA 7.0+_ (__TODO__: verify)
  * Any host compiler restrictions your version of CUDA may impose also apply
  here. For the newest CUDA version, this information can be found in the
  - [CUDA installation guide](http://docs.nvidia.com/cuda/cuda-installation-guide-linux/index.html#system-requirements)
  -
  + [CUDA installation guide](http://docs.nvidia.com/cuda/cuda-installation-guide-mac-os-x/index.html)
  In addition, if you want to contribute code to Ginkgo, you will also need the
  following:
  