Diego fix logic display questions

[DiegoOTdC]

The Problem
When the user finishes an exercise it would go to the second exercise in level 1 but then go back to the first question. It wouldn't continue to the question in level 2.

Steps to fix this

• Check if any exercise of the "allCurrentExercises" are already finished -> would be inside "completedExercises"

• push the exercises that match into a new array; "commonElements"

• create a leftOverExercises array where all of the commonElements are filtered out of the allCurrentExercises, so that you have an array with exercises that still need to be finished by the user.

• use if statement to check if there are still exercises to be finished -> otherwise show "you are finished"

• Create removeQuizQuestions in the store/exercise actions/reducer

• Create removeCompletedExercises in the store/user actions/reducer

• Add removeQuizQuestions and removeCompletedExercises in a dispatch to the homepage, so that every time the store will be empty when you go back to the homepage. ->Otherwise when you go finish an exercise and go to home, then go to the next exercise, instead of 3 you will see 6 questions.

• remove all unnecessary code (like dispatch(getExerciseById()) on the QuizCode page)

[DarianRushworth]

It looks really great, The remove actions and reducer logic is super smart for what we needed, Well Done!