EDU-13 Post module exam

[TylerSchaefer4]

POST /modules/:moduleId/exams/:examId/submissions (Make this similar to the route you designed for the get request)

this endpoint should accept the user's answers, evaluate them, update the user's score (this will reference the moduleExamScores json structure within the users table. Add a json to this value along the lines of {moduleId: X, moduleExamId: Y, score: int}), and return the result to the user.