need to require all the files in Rails application

If I don't add all these files to my `config/application.rb` I get various name errors during `ActiveHook::Hook.new` and `hook.save!`:

```ruby
require 'activehook/hook'
require 'activehook/redis'
require 'activehook/config'
require 'activehook/app'
```

I think each file in in `lib` should require whatever other file it needs.