whsc: ask for the approver's email address
whsc: default the approver's email address to the last cart
Merge remote-tracking branch 'origin/master' into whsc-approver

Conflicts:
	spec/features/whsc_proposal_spec.rb
Merge pull request #141 from 18F/whsc-approver

[#84702440] add field for approver email to WHSC form