Subjects API and some refactor

API url is now a subdomain. Must put `api.uno.dev` in hosts file

```api.uno.dev/v1/<resource name>```

Some un-DRY code in `Subjects` controller - the `RecordNotFound` exception.

 I don't see the need to create a Service as of the moment. It's pretty straightforward CRUD.
Hmmm, does `around_action :wrap_in_rescue` on the controller doesn't work?