Merge branch 'develop' of https://github.com/stan-dev/stan into develop
added raise_exception, compiles, tested by hand
added models for integration test
added tests for functions which throw exceptions
switched order of error checks, made error messages more consistent, updated unit test
cleanup - code for raise_exception stmts should be in branch issue-748, not in this one.
stan models that test error detection, error message
cleanup - wrong branch for these test models
Merge pull request #785 from stan-dev/bugfix/issue-579-vec-to-array-msg

Bugfix/issue 579 vec to array msg