add database field for ordering approvers
add method to retrieve approvers by position
only order approvers by position for linear groups
group #approvers specs
made Dispatcher module in preparation for linear flow support
convert dispatcher to a class

makes subclass methods easier to work with
make approval delivery method name more clear
validate UserRole#role
copy the position into the approval
add LinearDispatcher (incomplete)
throw error if model creation fails in specs
store the flow on the cart
add linear approval integration spec
make a helper for getting email delivery recipients
refactor linear approval spec
email subsequent recipient when approval is received
Merge remote-tracking branch 'origin/master' into linear-emails-B

Conflicts:
	app/models/cart.rb
rename cart creation spec w/ existing approval group
DRY cart creation spec
assign the flow on a cart from an existing approval group