admin: create admin user, rspec tests, and model validations
admin: db populate with Julia as an admin
admin: add admin sign_in to home page
admin: list of students
admin: create list of teachers
admin: create and delete languages from the system
admin: create and delete levels
admin: create and delete intents
admin: create and delete years_teaching
admin: create and delete certification levels
admin: create and delete durations of stay
language-classes: add migration and rspec
language-classes: add rspec and model validations
sample-data: populate sample students and teachers only in development
language-class: language_class belongs_to a student
language-class: add basic language-class controller and new view
language-class: use datetime_select
language-class: create language class
language-class: validate location and start_time
language-class: add ability for admin to see all language classes