refactored db seeds a bit

- Cleaner syntax for creating sections in courses
- used ‘password’ and ‘password_confirmable’ fields in the User seeds,
rather than using the encrypted_password.  Just to abstract things out
and follow how the User model would be used “in real life”.
- added some other fields to the local user seeds — first_name,
last_name, and email.
- used named symbols (i.e. :admin) for the user roles rather than an
integer.  This is just to increase readability
Merge branch 'master' of github.com:cit-jmu/workshop