Fix category feeds; add specs
Move rendering test
Add more assertions for category XML
Add Marketplace to NewsStory sources

This was added to accommodate a requirement that the Business Vertical
should feature some Marketplace content, but the PMP database wasn't yet
getting real content flowing through it, so this "marketplace" source
was an interim solution.
Cleanup
Add safe obj_key lookup
Remove CONTENT_CLASSES constant
Switch to postmark-rails gem
Make ContentMailer more secure; move to background job
Set FROM address to sender's e-mail
Revert "Set FROM address to sender's e-mail"

This reverts commit 6f4a090cb0345a43e5c718b47823776cae0d89ec.
Remove reference to old constant
Add some feature specs for content email
Merge pull request #187 from SCPR/content-mailer-updates

Content mailer updates
Merge remote-tracking branch 'origin/master' into rails4

Conflicts:
	Gemfile
	Gemfile.lock
	config/environments/production.rb
	spec/controllers/category_controller_spec.rb