added migrations and model for assignment categories
added route for creating new assignment category
added link for creating new assignment category
added migrations for assignment categories
created assignment categories controller
added views for assignment category index and new
added view for editing an assignment
added route to update all assignment categories
added styling for flash errors
changed display method for student percentage
added error message for categories that do not add up to 1
deleted test code
deleted test code
added methods to determine worth and earned points per student
changed else to return n/a in grade calculation method
deleted test code
changed display for student percentage
changed display for student percentage
added functionality for teacher to change assignment category names and weights
added functionality to display assignment category