message: mention correct node version
diff: Installing AutoRest on Windows, MacOS or Linux involves two steps:
  -1. __Install [Node.js](https://nodejs.org/en/)__ (6.9.5 or greater)
  +1. __Install [Node.js](https://nodejs.org/en/)__ (7.10.0 or greater)
  > for more help, check out [Installing Node.JS on different platforms](./developer/workstation.md#nodejs)
  2. __Install AutoRest__ using `npm`
  