Switch the mailers to be invoked using ids, not model objects. This makes it easier to support asynchronous mail jobs, as only simple ids need to be persisted.

Fixes #2808
Really use taxon name in taxons/show.html.erb

Really fixes #2814
Find visible select2-input element within promotion_adjustments_spec
Fix issue where, if using routing-filter, taxon autocomplete would break

Fixes #2248

This is due to the URL provided by spree.admin_search_taxons_url returning something like http://localhost:3000/admin/taxons?locale=en and then the code was appending '?ids=1' to the end of this, which is obviously an incorrect URL.

This new solution is more bulletproof.
Fixes #2788 allowing use of config.threadsafe!

Fixes #2852
Don't configure ActionMailer settings if they're already configured

Fixes #2855
fixes jstree ordering problem with jquery 1.9

Fixes #2728
ActionMailer::Base.smtp_settings in MailSettings spec
Dont need to run rake test_app.

Conflicts:
	CONTRIBUTING.md
Update selenium-webdriver to run with latest Firefox, bump Capybara and
rspec-rails versions too.

Also in this commit are a number of changes to the test running documentation.

Conflicts:
	CONTRIBUTING.md
	README.md
	backend/spec/spec_helper.rb
	common_spree_dependencies.rb
	frontend/spec/spec_helper.rb
Run 'bundle check || bundle install' to ensure dependencies are installed before build.sh
Use jsuri for products/new prototype selector too

Related to #2248
Fix tax calculator with non-VAT taxes.

This is an issue with Spree line items and tax rate calulators.

The method used to subtract tax from a VAT did not play nicely
with non value added taxes.

Fixes #2870
Pass args to provider method with send in Spree::Gateway#method_missing

Change-Id: Iff96153001cb3237b7a6cfe4bec3c25e086ec784

Fixes #2872
Bump to selenium-webdriver 2.32.0
[api] Don't set taxon.parent_id in Api::TaxonsController if parameters contain parent_id

Fixes #2757
Recalculate product count_on_hand when ANY of its variants are saved

Fixes #2799
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