Update required Go version in README
Update required Go version in README

Closes: #668

Signed-off-by: Jonathan Yu <b68e5eb3795f1ac579c1d61adea183f48bee1da1@redhat.com>

liggitt/source-to-image,PI-Victor/source-to-image,coreydaley/source-to-image,openshift/source-to-image,soltysh/source-to-image,guangxuli/source-to-image,dobbymoodge/source-to-image,dobbymoodge/source-to-image,mfojtik/source-to-image,gabemontero/source-to-image,rhcarvalho/source-to-image,PI-Victor/source-to-image,bparees/source-to-image,soltysh/source-to-image,mfojtik/source-to-image,jim-minter/source-to-image,jim-minter/source-to-image,mfojtik/source-to-image,bparees/source-to-image,gabemontero/source-to-image,PI-Victor/source-to-image,rhcarvalho/source-to-image,bparees/source-to-image,bparees/source-to-image,soltysh/source-to-image,guangxuli/source-to-image,mfojtik/source-to-image,guangxuli/source-to-image,PI-Victor/source-to-image,openshift/source-to-image,coreydaley/source-to-image,coreydaley/source-to-image,csrwng/source-to-image,openshift/source-to-image,coreydaley/source-to-image,gabemontero/source-to-image,dobbymoodge/source-to-image,rhcarvalho/source-to-image,csrwng/source-to-image,liggitt/source-to-image,dobbymoodge/source-to-image,rhcarvalho/source-to-image,gabemontero/source-to-image,guangxuli/source-to-image,jim-minter/source-to-image,liggitt/source-to-image,csrwng/source-to-image,jim-minter/source-to-image,soltysh/source-to-image,csrwng/source-to-image,liggitt/source-to-image