Investigate if using nbgitpuller possible for AGC demos

[matthewfeickert]

At the moment getting the AGC up and running on US Analysis Facilities is easy, given that it is just a simple git clone. However, today I learend about nbgitpuller, which

... lets you distribute content in a git repository to your students by having them click a simple link. Automatic merging ensures that your students are never exposed to git directly. It is primarily used with a JupyterHub, but can also work on students' local computers.

So if an analysis facility would set up nbgitpuller in their JupyterHub instance then it should be possible to have a link/badge on the AGC repo that people can click to launch into the AGC on a particular analysis facility. (Think something like mybinder but with persistent storage.)

@oshadura, if you and @alexander-held think this is at all interesting would you be able to deploy this at a coffea-casa to test?