Typo in storage spec
Fix thread safe issues with storage spec

Changing the class variable affected other spec. Also in specific specs we had
invalid repos as values and this also affected other specs.
Add TranslationRepository::Base#reload
Add override of #reload for TranslationRepository::Mo
Add override of #reload for TranslationRepository::Yaml
Add override of #reload for TranslationRepository::Chain
Add FastGettext.reload!

Calls reload on all repositories and clears the cache.

Closes #17.
Merge pull request #55 from skroutz/reload

Implements reload on all repositories and the storage engine