Added new persistent sampler that does not change the chain state, useful for forward sampling using generated quanities only
Merge branch 'develop' into feature/persistent_sampler

Conflicts:
	make/tests
Fix broken test, update doc
making test clearer
Changed name from persistent sampler to fixed parameter sampler
Merge branch 'develop' into feature/persistent_sampler
Updated tests
Merge branch 'feature/persistent_sampler' of github.com:stan-dev/stan into feature/persistent_sampler

Conflicts:
	src/test/mcmc/fixed_param_sampler_test.cpp
Working empty sampler test
Unified interface for autodiff'ing models
Fix model functional to work with higher-order autodiff by specifying template parameters; add test
Remove domain test for the moment
fixes issue #464
added diag_post_multiply to signatures and tested compilability
added acknowledgement for bug report
updated command and base_hamiltonian to catch std::exception instead of std::domain_error to catch all Boost math and Stan throws, fixes #476
added tests for pre/post multiply, fixed bug in post multiply
added pre/post-multiply tests for agrad matrix rev
Merge branch 'develop' into bugfix/issue-464-diag_pre_multiply
moving test files