Enable Gist API to pull content directly by filename

I think it would be really helpful to have the ability to specify a file name in a Gist API GET call, such that you could directly pull content in the same fashion as the repository content.

e.g. api.github.com/gists/gist_id/contents/filename

This would make Gist API calls amenable to the multitude of functionality that expects a ‘content’ returned by the API request.