update rack-oauth2 version
update rack-oauth2 version

gbirchmeier/openid_connect_sample,nov/openid_connect_sample,calh/openid_connect_sample,calh/openid_connect_sample,gbirchmeier/openid_connect_sample,nov/openid_connect_sample,nov/openid_connect_sample,gbirchmeier/openid_connect_sample,calh/openid_connect_sample