move CartItem initialization code out of Cart#import_cart_items
refactor Cart#process_approvals_without_approval_group
move CSV methods into CartItem
refactor Cart#create_comments_csv
refactor TimeHelper
abstract setting of multiple properties
create service object for exporting CSVs
make smaller methods in Cart
split up exporter
Merge pull request #113 from 18F/refactor-cart

[#82417004] refactor Cart
remove flow option feature flag
Merge pull request #114 from 18F/no-linear-flag

remove flow option feature flag
add mail_view gem
simplify CommunicartMailer#cart_notification_email signature
add mail previews for other mailer methods
fix approval email formatting

resolve 83329522
Merge pull request #115 from 18F/mail-view

add mail_view for email previews
Generalize Table spacing
Clean up earlier changes
clean up HTML problems