Adds support for non-American date formats

The domain us.battle.net uses mm/dd/yyyy format, everywhere else uses dd/mm/yyyy format. This
moves the date conversion from Achievement to AchievementScraper to add logic for region detection.

This is currently lacking a VCR cassette for the new spec because EU battle.net is down.  Once it's back up and I can store the cassette to pass the broken test, it will be ready.  Fixes #17 .