Remove dead non-file views in development mode on next request

We don’t currently track views in development mode which are using a string rather than a file. With #11, cleanup would happen on next app boot but it would be nice to do it on next request.

Perhaps `ActiveRecordViews.register_for_reload` on the model file itself would work? Might have to look at `caller` in `is_view` to work out the filename.
