Revise localized agreements

This is a very rough draft of revising the way we're localizing the agreements after the discussion following https://github.com/mozilla/fxoss/issues/199#issuecomment-51694614. Will utilize the "Ready for Review" label when appropriate.
I wanted to test this part of the functionality in isolation, because that's the only part of the view logic that's supposed to change. Because the rest of the changes to the view were only a minor refactoring, I thought it would be easier to verify that no unintended behavior changes were occurring  due to the refactoring by leaving those tests alone for this PR-- I'd like to refactor the rest of the tests too, but thought that would make more sense as a separate PR.