Fixed references in the README to old generators
Fixed references in the README to old generators

openeducation/clearance,benlivermore/clearance,benlivermore/clearance,sferik/clearance,thoughtbot/clearance,naveed-ahmad/clearance,pedrosmmoreira/clearance,janusnic/clearance,pedrosmmoreira/clearance,zernie/clearance,naveed-ahmad/clearance,naveed-ahmad/clearance,janusnic/clearance,benlivermore/clearance,zernie/clearance,pedrosmmoreira/clearance,thoughtbot/clearance,janusnic/clearance,thoughtbot/clearance,zernie/clearance