adding clear_chain to sampler
adding clear_chain to sampler

jellis18/emcee3,willvousden/emcee,ipashchenko/emcee,elkingtonmcb/emcee,pkgw/emcee,dfm/emcee3,dfm/emcee,willvousden/emcee,johnbachman/emcee,johnbachman/emcee,ga7g08/emcee,dfm/emcee,farr/emcee,linan7788626/emcee,drphilmarshall/emcee,ipashchenko/emcee-x,joezuntz/emcee