Fixed and streamlined Mac Neuronvisio installation

Hi Michele, 

I went through the installation procedure again, this time on my own macbook pro (I almost always use my Ubuntu boot on it though in part because of the struggle installing things on Mac!), and found a few pip packages that I had missed in my instructions. I also found that you can avoid having to download sip and PyQt separately if you supply the right options to the brew vtk install, which makes the whole process quite a bit smoother.

Sorry to have missed your latest release, but I can confirm that the Mac installation procedure is pretty solid now. However, I did run into a few bugs when trying to load models from ModelDB and use the time slider, which I will email you about separately.

Cheers,

Tom