remove deprecated .all finder

Running the current rails4 branch against my rails 4.0.0 application I get the following deprecation warning. 

DEPRECATION WARNING: Relation#all is deprecated. If you want to eager-load a relation, you can call #load (e.g. `Post.where(published: true).load`). If you want to get an array of records from a relation, you can call #to_a (e.g. `Post.where(published: true).to_a`). (called from available_locales at /Users/adamd/tmp/i18n-active_record/lib/i18n/backend/active_record/translation.rb:76)