Added Roles, Attendance Updates

Added the following roles: Admin, Professor, TA, Student, and Observer.

Made some good progres with the Attendance queries with the new sections_users_roles many to many to many table. I can now query for the students, tas, and professors of a class and display them. The next thing is to allow attendance to actually be taken.
Oops

Forgot to add this file on the last commit. It's used primarily in the seeds.rb file, but also in queries throughout the app so we don't have to remember, say, the role id for a Professor.