Updated engine for Spree 2.

- Drop support for 1.8.7
- New engine based on Spree 2.
- Bump version to 1.2.beta.
Deleted locale en-US in favor for en.

This locale is unessisary when only one translation key exists.
Updated locales with Spree namespace.
Moved controller decorator under admin.
Updated spec helper.

- Fuubar for spec runs.
- Simplecove and coveralls.
- Standard updates for Spree 2 tests.
Add locale spec.
Cleanup specs.
Minor code formatting and 1.9 hash syntax.
Changed travis and readme for testing.