netcoreapp1.1 support

Moving to netcoreapp1.1
```csharp
    "netcoreapp1.1": {
      "dependencies": {
        "Microsoft.NETCore.App": {
          "version": "1.1.0-*",
          "type": "platform"
        }
      }
```
Causes issues as the generated project.json puts it back to `netcoreapp1.0`