removed std::cout in print_progress; called the fully specified print_progress in run_markov_chain, removed defaults out of run_markov_chain
removed std::cout in print_progress; called the fully specified print_progress in run_markov_chain, removed defaults out of run_markov_chain

stan-dev/stan,stan-dev/math,stan-dev/math,stan-dev/math,stan-dev/stan,stan-dev/stan,stan-dev/math,stan-dev/stan,stan-dev/math,stan-dev/math,stan-dev/stan,stan-dev/math,stan-dev/math,stan-dev/math