During the course of the fundraiser, a student will have many reading sessions that will contribute to their overall amount of time they have spent reading.
[x] Create a reading_session model
[x] Refactor student.rb to update its' mins_read based on their reading_sessions
[x] Refactor teacher.rb to update a student's mins_read when adding a reading_session
During the course of the fundraiser, a student will have many reading sessions that will contribute to their overall amount of time they have spent reading.