Specs and fixes

This is for Spree master branch.

- [x] Add specs and test tools, was 1% now 97% coverage.
- [x] Fixed missing translations and translated mails.
- [x] Add Swedish locale.
- [x] Fixed assets paths and engine issues (mainly for tests to run).
- [x] Updated README.
- [x] Add Travis badge and config.

It was actually quite broken, now only the Captcha integration need some additional attention.