Restructured editing/deleting comments for polymorphic relationships.

-Because of the CommentsController method is now called upon from different sources, restructured the methods to fit all types of requests
-show, create, edit, and update now utilizes a conditional statement, which checks for the source of the inputs: Video and Playlist (will be adding Comments later)
-Now routes the form to the correct path utilizing @comments_origin, @comments, @edit_path, and @destroy_path. These variables will already know which route to take due to the conditional statement.
-Restructured the show.html.erb file to fit a the new structure.
-Ran and passed a full testrun of adding/deleting/editing all playlists/videos/and comments.