Store server.key.enc and server.key consistent to trailhead

@clairebianchi :

Working on the Super session demo and using the yml template. One thing I noticed is that in the trailhead we put the server key file in an assets folder but in the yml template we save it directly to the project folder. I would like us to be consistent.

@mayanktahil :

The encrypted server.key.enc file should be in the assets folder based on the trail head. I wanted to make sure the non-encrypted server.ley isn't in the repo. I kept the encrypted server.key.enc in assets because that's how it was showcased/demo in the other trailheads (The one with Travis and GitHub I think).

I see in the CI Yaml there is a step to decrypt the server.key.enc file that outputs it to server.key in the repo's root folder I think that's expected. However the input for the .enc file is also assumed to be in the root repo directory, not assets. See this line. Maybe we just need to update that line to take the input from assets/server.key.enc to stay consistent?

cc: @francispotter