Rails 6.0 introduced a `hosts` option which, in the development
environment, defaults to all IP addresses and the `localhost` domain.
However, we can't work with subdomains using `localhost`. For that
purpose, the `lvh.me` domain was created [1].
So we're allowing this domain and its subdomains so we can use them
while working with multitenancy in the development environment.
[1] http://railscasts.com/episodes/123-subdomains-revised
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