To upstream

I have been maintaining my own fork for a while, better to push it upstream. These commits are updates to use with Spree master branch, can probably be back-ported all way back to 2-0-stable. I submit them as a collection instead of one single commit but it does not really make them independent from each other (pls don't squash).

I recommend you to create a `1-2-stable`/`1-3-stable` branch for your current code and then use this for `master`.
I have bumped this to `2.0.0.alpha` to keep good separation.
Only one test is failing `:enqueue return order only once not twice` at `./spec/models/order_spec.rb:30`I have no clue how to solve it for the moment.

The commits include:
- [x] Add Swedish locale (depends on Spree namespace).
- [x] Updated README and LICENSE.
- [x] Removed no longer used Versionfile.
- [x] Updated engine for latest Spree version (master branch).
- [x] Add manifest assets (or feature specs breaks etc).
- [x] Updated test environment.
- [x] Use `.add_routes` not `.draw`.
- [x] Strong parameters fix by @kenjinino
- [x] Spree i18n namespace scope style.
- [x] Fixed specs syntax and failures.
- [x] Assign a default taxon if the product is not associated with a category by @iloveitaly (hope this change valid?)
- [x] Fixed `order.completed_at` issue if `nil`
- [x] `Spree::Order` `tax_total` replaced with new `included_tax_total` (may also be `additional_tax_total`)
- [x] Use `bin/rails` instead of `script/rails` for Rails4 branches.