validate Approval#status
simplofy signature for CommunicartMailer.approval_reply_received_email
remove usage of arbitrary param hash for approval email
remove use of @cart_template
move cart template logic into decorator
remove use of ternary operator

...for better readability and test coverage reporting
unify approval logic
add code climate badges
fix rubocop lint warnings
Merge pull request #89 from 18F/badges

add Code Climate badges
Merge pull request #90 from 18F/rubocop

fix RuboCop lint warnings
Merge remote-tracking branch 'origin/master' into approval-refactor

Conflicts:
	app/models/cart.rb
Merge pull request #88 from 18F/approval-refactor

Approval refactoring
Merge branch 'master' into 81500686_add_user_after_oauth

Conflicts:
	app/controllers/application_controller.rb