Users can delete posts

Add delete button to posts show page

Add destroy route under show resources

Controller deletes post of whatever post_id is receives then routes to
post category
Only users who made a post can delete it

Add authentication method to user model and implement it through application controller

Post controller uses before_action to authenticate before destroy action
Must be admin OR post creator to delete a post

Remove flash messages from application controller

Give all before_actions redirect_to methods

Extract application controller methods to user model
Delete button does not appear for unauthorized users
Refactoring:Add flash messages.Remove instance variables

1) Add flash messages back into Application controller

2) Remove useless instance variables from posts#destroy

3) Extract login authentication from ApplicationController into only
PostsController
Refactor git conflicts in posts/show