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
Use proper gradient template parameters
Merge branch 'develop' into feature/uniform_autodiff_pattern

Conflicts:
	.gitignore
	make/tests
	src/test/CmdStan/command_test.cpp
Merge branch 'develop' into feature/persistent_sampler

Conflicts:
	make/tests
Merge pull request #353 from stan-dev/feature/persistent_sampler

Feature/persistent sampler
Merge pull request #459 from stan-dev/feature/uniform_autodiff_pattern

Feature/uniform autodiff pattern
Merge branch 'develop' into feature/issue-427
Add unit test for refresh=0 and refresh>0