propagate script name through snippet library

[tkphd]

In Ep. 13, I made the change to the script filename (new_name to hello-world) because learners and inexpert instructors are more likely to just type what's there than to come up with something on the fly, and "new name" is a terrible title. However, the snippets retain the old name, causing confusion. The fix is to update the job names in all the snippets.