Return html_safe strings from variant_price_diff

Fixes #2737

Conflicts:
	core/app/helpers/spree/products_helper.rb
Explicitly setting taxon edit path in the form

If not made this way then taxon.permalink is used in the url model thus raising unknow path error.
add failling test for https://github.com/spree/spree/issues/2823

Fixes #2869
When using Russian Rubles, display the full currency symbol rather than just '.'

Fixes #2737
Remove backend+frontend from .travis.yml, add promo

That's what I get for blindly copying it over from the master branch
Backend shouldn't exist in 1-3-stable
Rescue from DestroyWithOrdersError only if it's defined

Fixes #2877
[cmd] Ensure there is a linebreak before gem lines inserted before installer

Fixes #2798
Allow the description to go straight to the page raw.

Fixes #2874
Make OrderPopulator error messages translatable

Fixes #2845
[sample] Remove duplicate master variants for ror_baseball_jersey and spree_baseball_jersey products

Fixes #2783
Don't show coupon code field if there are no promos with coupon codes

Fixes #2835
Fix page action button style when method is put.

Fixes #2880
set position for a Variant object on creation

Fixes #2744

Conflicts:
	core/app/models/spree/variant.rb
Revert use of display_price in data-price attribute for _cart_form

Fixes #2886
Update admin/shipments/{index,edit}.html.erb I18n scopes to use shipment_states,
not state_names.

Fixes #2888
Update admin/shipments/{index,edit}.html.erb I18n scopes to use shipment_states,
not state_names.

Fixes #2888
Fix resource_controller update_positions test
API - Fix missing translation for 'invalid taxonomy id'.

Invalid taxonomy id was not translated.
Account for current_order returning 'nil' in OrdersController#update

Fixes #2750

Conflicts:
	core/config/locales/en.yml
	core/spec/controllers/spree/orders_controller_spec.rb