switching readme to rst
switching readme to rst

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