README.md: add notes to How to compile on Windows

Jud White

2018-03-25 c6ecf1e0420737eafeb99b27b1d716b46a6cbb7a

 src/network_kernels.cu

@@ -121,7 +121,7 @@
   }
#endif
    forward_network_gpu(net, state);
   cudaStreamSynchronize(get_cuda_stream());
   //cudaStreamSynchronize(get_cuda_stream());
    backward_network_gpu(net, state);
}