Fix tax zones country selects styles (remove button was under select)

[Fixes #3418]
Bump to Rails 3.2.14
Update rails version in README [ci skip]
Move Error Text calculation inside error block
Bump caypbara to 2.1.0:

* Add timeout into config/database.yml template to avoid SQLite3 DB locked out
* Use lenient non-exact setting for Capybara element matcher (same as 1.x)
Fix Frontend specs for capybara2.
[sample] Provide feedback when loading images

This can take a long time due to Paperclip doing its thing for all the different image styles.

Fixes #3395
[backend] Associate user with an order when NOT using guest checkout

Fixes #3335
Doesn't create redundant taxons root items.

Fixes #3413
Fixes #3417
extract searcher_class instantiation into module

searcher_class was being instantiated in the same way in home_controller
products_controller, and taxons_controller. This moves that code into a
new Spree::Core::ControllerHelpers::Search module.

Fixes #3420
Allow unshippable items on the order

So that users don't have their cart emptied every time they checkout to
payment in a store that doesn't have a delivery step

Fixes #3193
Wait for ajax from stock level population to complete in order_details_spec
Remove frontend's version of admin/plugin/fontawesome

This should only exist in backend
Remove old version of fontawesome from backend's app/assets and use the one in vendor/assets (with proper font-url usage)

Fixes #3424

Conflicts:
	backend/app/assets/stylesheets/admin/plugins/font-awesome.scss
Correct include for font-awesome
Correct payment_status checks in payments_spec
[backend] Fix one more case of to_not raise_error(SpecificError) in image_settings_spec
[frontend] Remove specific error check in currency_spec
Never allow AR's connection's open_transactions to dip below 0

Stopgap for #3428

Conflicts:
	backend/spec/spec_helper.rb
	frontend/spec/spec_helper.rb
Font Awesome font-url() not respecting asset_host

Going back to the ERB version of Font Awesome but
actually using the correct #font_path helpers.

Fixes #3429