emails: disallow names ending with a period.

Update email validation rules to disallow the percent character (e.g.
`foo%bar@gmail.com`) and names ending with a period (e.g. `foo.@gmail.com`).
Names ending with a period are invalid according to the RFCs and cause
`Mail::Address.new` to raise an exception.

The percent character is technically legal, but only one email used it
and it was probably a typo.

test/unit/email_address_test.rb

@@ -51,6 +51,7 @@ class EmailAddressTest < ActiveSupport::TestCase
       assert_equal("foo@gmail.com", EmailAddress.new(address: "foo@g,ail.com").address.to_s)
       assert_equal("foo@gmail.com", EmailAddress.new(address: "foo@gmai;.com").address.to_s)
       assert_equal("foo@gmail.com", EmailAddress.new(address: "foo@gmail@com").address.to_s)
+      assert_equal("foo@gmail.com", EmailAddress.new(address: "foo.@gmail.com").address.to_s)
     end
   end
 end