update readme.md for clblas-2.8.0 branch, and visual studio 2015 build notes
update readme.md for clblas-2.8.0 branch, and visual studio 2015 build notes

hughperkins/DeepCL,hughperkins/DeepCL,hughperkins/DeepCL,MiniLight/DeepCL,MiniLight/DeepCL,hughperkins/DeepCL,MiniLight/DeepCL,MiniLight/DeepCL,hughperkins/DeepCL,MiniLight/DeepCL