Added vNext package

vNext is an ST3 extension for building ASP.NET vNext apps.

![screenshot 2014-07-17 19 31 06](https://cloud.githubusercontent.com/assets/4734691/3621972/038820fa-0e24-11e4-91d2-00f87e40cba8.png)

The video contains more information
https://www.youtube.com/watch?v=0Uv8l1RS5zA