remove update apparatus option
remove update apparatus option from UI.
stick to one 'assign_to' method.
fix duplicate bug for students and teachers methods.
re-route students to main menu from unenroll method
adjust wording in student section for more intuitive UI.
add method show_teachers to class Teacher to list all teachers and their apparatuses
adjust wording on show_teachers spec (Teacher class).
add content to README.md file.