Changed Skills to be polymorphic in both the migration and model files. Edited Students and Professor to reflect the polymorphic relationship with Skills.
Removed CreateSkillsJoinTable migration file to replace it with a new Skills migration file.
Created Skills migration. Deleted AddHouseIdColumnToStudents migration. Modified Students migration to include a :house_id.
DB migration.
Edited Skills Migration and Model to belong_to Spells.