Upgraded VSIX to support Visual Studio 2013
1.Upgraded solution to VS2013 and VS2013SDK
2.Added VS version 12 as target
3.Upgraded NuGet dependency to 67e54e40-0ae3-42c5-a949-fddf5739e6a5
4.Upgraded Nancy to 0.21.1
5.Upgraded C# project files hint path to use solution dir
6.Upgraded C# template zip files