Add note to install docs about setting auth.user-registration
Add note to install docs about setting auth.user-registration

Because I missed this and then tsuru was failing to create an admin user
and I puzzled over this for a while before I figured it out.

gciotta/tsuru,tsuru/tsuru,guilhermebr/tsuru,cgvarela/tsuru,gwmoura/tsuru,kgrvamsi/tsuru,cezarsa/tsuru,jblancett/tsuru,gwmoura/tsuru,Endika/tsuru,cezarsa/tsuru,firebitsbr/tsuru,mderaldo/tsuru,RichardKnop/tsuru,ggarnier/tsuru,ggarnier/tsuru,tuxmonteiro/tsuru,firebitsbr/tsuru,ggarnier/tsuru,jblancett/tsuru,Endika/tsuru,tsuru/tsuru,mderaldo/tsuru,cezarsa/tsuru,jblancett/tsuru,hcxiong/tsuru,ggarnier/tsuru,guilhermebr/tsuru,ArxdSilva/tsuru,tuxmonteiro/tsuru,cezarsa/tsuru,ArxdSilva/tsuru,4eek/tsuru,kgrvamsi/tsuru,gciotta/tsuru,cgvarela/tsuru,tsuru/tsuru,RichardKnop/tsuru,gciotta/tsuru,4eek/tsuru,firebitsbr/tsuru,guilhermebr/tsuru,4eek/tsuru,ArxdSilva/tsuru,cgvarela/tsuru,ArxdSilva/tsuru,guilhermebr/tsuru,RichardKnop/tsuru,gwmoura/tsuru,hugoantunes/tsuru,kgrvamsi/tsuru,Endika/tsuru,tsuru/tsuru,mderaldo/tsuru,hcxiong/tsuru,tuxmonteiro/tsuru,hugoantunes/tsuru,hcxiong/tsuru