structure check refactored, with special handling of 'activerecord.errors.messages.restrict_dependent_destroy' key
en and ja locale fixes for 'activerecord.errors.messages.restrict_dependent_destroy' key
translations completed for locales: hr, bs, sr (and scr), readme updated
fixed 'restrict_dependent_destroy' key in pt-BR
Add temporary matchers for the irregular key names of Rails 4.0.0

Rails 4.0.0 introduced the following new keys:
  - errors.messages.restrict_dependent_destroy.one
  - errors.messages.restrict_dependent_destroy.many
  - activemodel.errors.messages.restrict_dependent_destroy.one
  - activemodel.errors.messages.restrict_dependent_destroy.many
  - activerecord.errors.messages.restrict_dependent_destroy.one
  - activerecord.errors.messages.restrict_dependent_destroy.many

These key names are irregular from the point of view of i18n-spec.
It interpretes them as pluralization keys, but they aren't.

The new matchers treats them specially and can avoid false positives.

This commit closes #340.