Made it so user who is not signed in gets authentication message when trying to join a meetup
Added ability for users to leave a meetup they had joined.  Added non-functional comments form and comment table
Added ability to add comments to a meetup when signed in.  Added validations to only allow comments that have text in the body of the comment.
Made it so user must have joined a meetup to comment on it.
Added placeholder text for when there are no comments or attendees to show on meetup page.