Added Post Model, Post Controller, User can create posts!

  *belongs to a user
  *has content, id, user_id
  *created a create method for PostsController
  *Added A Post Route for user(show) and posts (create only)
  *Added A new post variable to user show
is content required? If so, why not `null: false`?
Also, Are you limiting the content to post to just 256 characters?