Revert "Merge pull request #64 from stan-dev/feature/mcmc_writer"

This reverts commit a0132a14c120266c6c2bc25c72242f44bb9951c2, reversing
changes made to e83baa2577f8abadede1f65a9ac2b0474de568ac.
Merge pull request #78 from stan-dev/feature/revert_pull_request_64

Revert "Merge pull request #64 from stan-dev/feature/mcmc_writer"