Expand data arguments; need to merge model_test_fixture fixes and run tests before making a pull request.
Merge develop
Update to use new data arg format
Merge pull request #215 from stan-dev/feature/expand_data_arg

Feature/expand data arg
Merge branch 'develop' of https://github.com/stan-dev/stan into feature/parser_error_reporting
Unit parser error tests now use the main parser