Remove i18n symbol dependency

date.order is the only key in rails i18n that is required to be a
symbol. This patch allows for symbols or strings which means:

* No requirement for symbol type in .yml files. A future
  YAML.safe_load wouldn't need to load symbols
* Rails could actually use json rather than yml as the backend
Don't change the original i18n data
Restore and adapt the implementation reverted at
https://github.com/rails/rails/commit/cc1c3c5be061e7572018f734e5239750ab449e3f

Now instead of raise, we log by default in development and test
Refactor ActiveSupport::Cache::Store#fetch.
Updated version of jQuery rails in gemfile
Merge pull request #9000 from sherwu/master

Updated Gemfile to use jQuery-rails v 2.2.0
Merge pull request #8081 from JoeyButler/refactor_cache_store

Refactor cache store
Merge pull request #8978 from chrismcg/remove_i18n_symbol_dependency

Remove i18n symbol dependency
Merge branch 'master' of github.com:rails/rails into transactions_memory_fix