Refactor for Spree 2-0-beta.

Been cleaning up this extension a bit to make it more in-line with Spree master.

- Updated the gem engine to what spree master is actually generating, so now you don't have to confirm install of migrations on every `bundle exec rake test_app`.
- Added database_cleaner and simplecov. It only has 6 request specs so I believe that more tests has to be written. Then simplecov can be removed again later when it has a better spec coverage.
- Heavy code formatting, I actually cant see any forks with major improvements so I think this is fine.
- Fixed structure for ALL locales and add i18n-spec to test this. Now all pass fine, before it was a big FAIL. I based structure on en.yml also add extra pluralization keys so it might not be correct in Russian and Polska.
- Fixed translations for Spanish and Portuguese ... pura vida ;)
- Added locales for Swedish.
- Removed H1 tag because many forks has done this.

Some not 100% sure changes.
- Version bump? I change a lot so why not but did I do it correctly?
- Removed 1.8.7 from being tested on Travis. It test all versions but this version is very 1.9.3 ruby stylish and I'm not sure how to fix proper Travis matrix.