title: Tags not showing for Wagtail under posts or /tag page
body: <p>I'm following this guide > <a href="http://docs.wagtail.io/en/v1.9/getting_started/tutorial.html#tagging-posts" rel="nofollow noreferrer">http://docs.wagtail.io/en/v1.9/getting_started/tutorial.html#tagging-posts</a></p>
  
  <p>As far as I can tell, I followed the guide exactly as it's written but tags won't load while viewing individual blog posts and the tag page doesn't show a list of tags. I'm not getting any errors, they just don't show up.</p>
  
  <p>They are showing when searching via link e.g. <a href="http://0.0.0.0:8000/tags/?tag=lorem" rel="nofollow noreferrer">http://0.0.0.0:8000/tags/?tag=lorem</a>.</p>
  
  <p>Thanks.</p>