No need to call gemspec in common_spree_dependencies

Each component Gemfile already calls it
Add ability to set page title for admin pages using a content_for :page_title
Leave comment as to why we need to do next_transition.run_callbacks in OrdersController
Only require email when past cart or address

This means that an email field can now be provided on either the cart or address forms

More importantly, the 'state' field will now say 'address' when users reach that state, rather than 'cart'

Fixes #4079
Call shared/_head title content_for 'title', becuase 'page_title' is already taken
Move shipments JS out of variants_autocomplete.js and into shipments.js
Showing line items on orders screen now when there are no shipments

Fixes #3958
Show a big warning when people use protected_attributes

A lot of people have been running into issues when protected_attributes is in use, mainly because it FORCES models to have attr_accessible declared on them. This is not the default within Rails 4 engines/applications, and so we run into major problems with Spree when this gem is in use.
Remove conflict from shipments.js.erb
Add index to source columns on spree_adjustments so UpdateAdjustmentStates migration does not take ages to run on large databases

Fixes #4145
Include tax_total in Order API responses

Fixes #4157
Fixes #4158
Added display_ship_total to order api response

Fixes #4161
Update changelogs for 2.1.4 release
[api] Split taxon_ids as they're passed to Products#create and Products#update
Don't use hard coded assets prefix

Fixes #4156
Bump activemerchant to 1.42.3
Remove variant default_scope from Price class this fixes Price must belong to a variant when trying to fetch the price fo a deleted variant

Fixes #4169
Bump to awesome_nested_set 3.0.0.rc.3
Fix states_required references for countries that don't actually need states

See:

* http://en.wikipedia.org/wiki/Address_(geography)#Switzerland
* http://bitboost.com/ref/international-address-formats/switzerland/
* http://geneva.angloinfo.com/information/housing/post-codes/
* http://en.wikipedia.org/wiki/Address_(geography)#Malaysia

And other online sources.  May need to review additional countries referenced in d0585271b7bc8a285b7ffdbeb1af45bdfece1e22
Add inverse_of to associations between shipping methods and rates

Fixes #4168