Compatibility with ActionView's lazy lookup

Translation keys beginning with '.' were taken as is by i18n_viz, not
generating the full key, making it quite useless.

This pull requests introduces the use of ActionView's method "scope_key_by_partial", used in the translate method to get the full scope automatically based on the current view.

Please note that this introduces a hard dependency on ActionView. If you wish to become Rails agnostic, a different implementation testing the existence of this method is necessary.