Revert "Merge pull request #1020 from ariddell/feature/remove-chains-add-method"

This reverts commit 8820ac2e7b4b239b46f3e2c6048b8a3d11ef3404, reversing
changes made to 575deeed77ef3bef9aff85b9d5da51f2bb2afed8.
Merge branch 'develop' of https://github.com/stan-dev/stan into feature/issue-867-more-fun-args