Unused keys

[alec-c4]

Hi, lads!
Could you add rake task for searching of unused keys?

[grosser]

sounds kinda useful ... should be easy to do during the rake gettext:find since it knows all old (existing) and all new (just parsed) ... so I'd start by opening the gettext gem and poking around in it's rake tasks ... the tasks should then ideally go into gettext gem to make it available to more uses