Add memoized interpolated_options and used it everywhere.
Merge remote-tracking branch 'origin/master' into interpolated_options

Conflicts:
	app/models/agent.rb
	spec/models/agent_spec.rb
take dsander's advice and use interpolated instead of interpolated_options
Merge pull request #382 from cantino/interpolated_options

Add memoized interpolated_options and used it everywhere.