Rethink the contact page

Since there is a form to be submitted, I’m no longer treating the page
itself as a resource. By focusing on emails instead, I can have a path
like /contact_emails/new, which seems to make sense.
Recreate the contact email form

Uses Rails form helpers. Might want to switch to them on the backend as
well.
Create AdminMailer

Use it to send contact emails. There are some problems with encoding.