create a ParallelDispatcher class
move mailer methods into dispatcher
clean up dispatcher spec
less setup for dispatcher specs
add validation on Approval#role
move approval notification emails into dispatcher
refactor approval relation methods
move param conversion out of model
move display_status logic into the cart decorator
make query for rejections more efficient
remove redundant clear of deliveries
Merge pull request #94 from 18F/dispatcher-B

create a ParallelDispatcher class, take two