Updated rails dependency to 4.1.6 (to match spree 2.4)
Updated factory_girl_rails dependency to 4.5.0 (to match spree 2.4)

Without this, the factories don’t work.
Fixed `active_shipping_settings_controller_spec.rb`

Remaining broken tests are caused by a regression in Spree::Core, where Spree::Package no longer knows about its order. Therefore, none of spree_active_shipping’s methods are able to call `package.order.ship_address`
Added regression tests for `package.order` and `package.stock_location`, to make sure correct values are available.

These depend on https://github.com/spree/spree/pull/5546
Update `weight_limits_spec` for `Spree::Stock::Package` now expecting inventory_units inside of new class `Spree::Stock::ContentItem`

6 specs still failing, centered around `Spree::Calculator::Shipping::ActiveShipping::Base.convert_package_to_weights_array`
convert to decimal