Add support for namespaces

We constantly have to edit package.json files and tsconfig.es5.json because we use a company namespace, examples: @cognitec/ui, @cognitec/authentication, etc.

When I want to use the generator, I am in .../@cognitec/ folder. I typically mkdir, example: mkdir ui then I run the generator, e.g. yo angular2-library and I enter in the name of the package, e.g. @cognitec/ui but this results in a flat module ID of cognitec-ui instead of what we need.

It would be wicked awesome if the generator was capable of figuring out from the package name that the user enters, e.g. @cognitec/ui, that the user is in the @cognitec folder and proceeded to create the ui folder, and package.json and tsconfig.es5.json files that contained @cognitec/ui as the package name and flat module ID.

Thanks for this excellent generator. It has been invaluable to us.