Clarifications to the Readme

Clarify that latest node 0.11.x may break your builds and that you may need VC++ 2010 SP1 on Windows, too.

By the way this is my first actual pull request :P

![I have no idea what I'm doing](https://cloud.githubusercontent.com/assets/2404138/3726122/ee01ee4a-168f-11e4-8834-b2848ce83147.jpg)