RFR- JL add email

users will receive emails when signing up for an account at OkBus, when they post a review, and when a review they authored is upvoted or downvoted.
You can do this in a single conditional.  If you create an `.authorized_to_edit?(review)` instance method on the `User` model, you could even shorten this to:

```erb
<% if current_user  && current_user.authorized_to_edit?(review) %>
  #...
<% end %>
```