You can safely delete it.
The file is used by the nodejs module v8flags for caching. If you delete it it will create a new one on next run.
I guess it was created because Gulp depends on v8flags and:
The ASP.NET 5 templates included in Visual Studio 2015 use Gulp, and they install Gulp into your project’s node_components folder so it’s all ready for you to use in your project.
https://msdn.microsoft.com/en-us/magazine/mt595751.aspx
Update: The new name of the file is .v8flags.{version}.{md5-hash-of-username}.json.