Add guidance
Add guidance

Add docs about skip_lookup and autocreate options being incompatible.
Add docs about publishing to a topic before a subscription is created.

swcloud/google-cloud-ruby,dazuma/google-cloud-ruby,googleapis/google-cloud-ruby,dazuma/google-cloud-ruby,blowmage/gcloud-ruby,hxiong388/google-cloud-ruby,swcloud/google-cloud-ruby,swcloud/google-cloud-ruby,hxiong388/google-cloud-ruby,landrito/google-cloud-ruby,landrito/google-cloud-ruby,CloudVLab/google-cloud-ruby,CloudVLab/google-cloud-ruby,CloudVLab/google-cloud-ruby,quartzmo/gcloud-ruby,CloudVLab/google-cloud-ruby,yancya/gcloud-ruby,gwmoura/gcloud-ruby,quartzmo/google-cloud-ruby,googleapis/google-cloud-ruby,landrito/google-cloud-ruby,quartzmo/google-cloud-ruby,quartzmo/google-cloud-ruby,quartzmo/google-cloud-ruby,CloudVLab/google-cloud-ruby,dazuma/google-cloud-ruby,qingling128/google-cloud-ruby,quartzmo/google-cloud-ruby,landrito/google-cloud-ruby,landrito/google-cloud-ruby,hxiong388/google-cloud-ruby,swcloud/google-cloud-ruby,dazuma/google-cloud-ruby,googleapis/google-cloud-ruby,googleapis/google-cloud-ruby,googleapis/google-cloud-ruby,qingling128/google-cloud-ruby,dazuma/google-cloud-ruby,qingling128/google-cloud-ruby,qingling128/google-cloud-ruby,hxiong388/google-cloud-ruby,googleapis/google-cloud-ruby,dazuma/google-cloud-ruby,quartzmo/google-cloud-ruby