Creates email digest mailer
Adds EmailDigest.deliver_latest
Removes spurious file
Order these by created_at too
Modifies delivery logic for #67

Closes #67
Email recipient is constant

Closes #68
Returns to using a partial
Merge remote-tracking branch 'origin/master' into email-digest

Conflicts:
	app/mailers/email_digest.rb
	app/models/email_digest_delivery.rb
	app/views/service_requests/show.json.jbuilder
	spec/mailers/email_digest_spec.rb
Merge pull request #74 from alindeman/email-digest

Merges changes I meant to add to the original PR