Fix delete link for taxonomies

since the Delete taxon url is look like this,
DELETE "/api/taxonomies/854451433/taxons558398399"
the delete process is not happening.
somebody missed a slash in between the 'taxon' and taxon_id

Fixes #2710
Mailers now require a from address, so we need to give defaults, using MailMethod.current

Conflicts:
	api/spec/controllers/spree/api/v1/shipments_controller_spec.rb
	core/app/models/spree/app_configuration.rb
Truncate product description when used as meta description

Fixes #2396
Fix jirafe admin settings styling

Fixes #2733
Move currnet_currency and ip_address helpers to ControllerHelpers::Order, where they're required
[frontend] tidy up let(:order) block in CheckoutController spec
Correct MailMethod usage in mail_interceptor, order mailer and shipment mailer specs
Added checked values for the radio_button_tag of currency_symbol. fixes #2755

Fixes #2756
Fix value of back_to_properties_list in en.yml

Fixes #2753
Don't require payment methods if payment isn't required
Re-add .travis.yml so we can get second opinions on builds
Check for spree.login_path, not spree.spree_login_path in unauthorized redirect

This fixes the issue where people going to admin WEREN'T being redirected to the sign in page
Revert "Check for spree.login_path, not spree.spree_login_path in unauthorized redirect"

This reverts commit fcda08552036b20a9866b189bd0e74ea8bef1830.

This causes the build to break:
http://ci.spreecommerce.com/viewLog.html?buildId=1533&buildTypeId=bt5&tab=buildLog

This is due to payment_required? calling update_totals all the time.
Revert "Revert "Check for spree.login_path, not spree.spree_login_path in unauthorized redirect""

This reverts commit 34bef72f714f939cda33e1047cc6b734363ecf33.

Wrong commit was reverted!
Revert "Don't require payment methods if payment isn't required"

This reverts commit 318b820114d6d631e9be6ddb500e6a234612407f.

This is causing build breakages:

http://ci.spreecommerce.com/viewLog.html?buildId=1533&buildTypeId=bt5&tab=buildLog

payment_required? is calling update_totals, which causes a massive callback
chain and ultimately results in these tests failing
Merge branch 'master' into develop