update instructions in README

Conflicts:
	metadata/replication_settings.go
Change-Id: I86357cb69005a086495e18eabfab13eb8a64f874
Reviewed-on: http://review.couchbase.org/44254
Reviewed-by: Xiaomei Zhang <xiaomeizhangatwork@gmail.com>
Tested-by: Yu Sui <ysui68@gmail.com>