Change manual setup instructions

The old instructions would fail on older versions of Git.
No one has complained about the Git commands in the create
script yet, though, so this updates the manual instructions
to more or less follow the exact same steps done by the
create script, including the same Git commands.

Now, instead of creating and cloning an empty repo, users
are instructed to create a new repo, but clone the workshop-template
repo and add their new repo as a remote.
For bonus marks, figure out how we can just call it 'check' (to be 
consistent with the workshop repo) but still import it into 
test_check.py (I kind of got it working with the 'imp' module, but only 
kind of), *and* not wind up with a file called 'checkc' containing the 
bytecode version of the file after running the tests.