Enable multi_gp in the language.
Add multi_gp to the manual.
Fix inverse in manual.
Fix function signature.
Add agrad unit tests for multi_gp_log.
Merge branch 'develop' of https://github.com/stan-dev/stan into develop
Merge branch 'develop' of https://github.com/stan-dev/stan into develop
removed std::cout and std::cin from dump.hpp, added ostream argument to print(), removed default constructor from both dump_reader and dump_writer
removed std::cout from the default arguments of test_gradients within model/util.hpp. common/command.hpp already calls it with streams
removing std::cout and std::cerr from stan/mcmc/*
changed implementation of covariance and correlation to throw exception instead of outputting to std::cerr
Merge branch 'feature/add-multi_gp' of git://github.com/mbrubake/stan into feature/issue-359-add-multi-gp
Merge branch 'develop' into feature/issue-350-add-multi-gp
Merge pull request #2 from stan-dev/feature/issue-350-add-multi-gp

Feature/issue 350 add multi gp
Move multi_gp gradient test to new folder
Merge pull request #3 from randommm/feature/multi-gp

Feature/multi gp
Merge branch 'develop' of https://github.com/stan-dev/stan into develop
removed CmdStan interface doc
updated doc and finished issue #567
updated version for stan-reference