running-coreos: update intro
running-coreos: update intro

bq-xiao/docs,joshix/docs,atxwebs/docs,ionave/docs,endocode/coreos-docs,jonboulle/docs,ksmaheshkumar/docs-2,iankronquist/docs,robszumski/docs,hkjn/docs-1,marineam/coreos-docs,coreos/docs,jdloft/docs,michelleN/docs,skynet/docs,mischief/coreos-docs,wli6/docs,mjg59/docs