Specs and fixes

- [x] Add more specs and better test support.
- [x] Updated Versionfile, README and add LICENSE file.
- [x] Let Travis run all branches.
- [x] Add missing locale keys + add Swedish locale.
- [x] Use `find_by_slug` not `find_by_permalink` for `Spree::Product`
- [x] Fixed additional deprecated finders (warnings only appeared with new specs).
- [x] `Spree::RelationType` `:name` and `:applies_to` should be required and `:name`
should be unique.
- [x] Use new `.add_routes` instead of `.draw`
- [x] Minor layout tweaks and additional standard hooks.

:globe_with_meridians: Note: that locale key `name_or_sku` is duplicate but the English original version as seen on [localeapp](http://www.localeapp.com/projects/4605/translations?utf8=%E2%9C%93&in_locale=13851&search=name_or_sku) actual has description in it _"Name or SKU (enter at least first 4 characters of product name)"_ so the keys are necessary override until fixed.

@radar @peterberkenbosch @jdutil :smiley_cat: ping!