Revert "Add "Today We Fight Back" banner"

This reverts commit 37399f2bc6.

app/views/layouts/_twfb.html.erb

@@ -1,5 +0,0 @@
-<!--[if !(lt IE 8)]><!-->
-  <script type="text/javascript">
-    (function(){var e=document.createElement("script");e.type="text/javascript";e.async=true;e.src=document.location.protocol+"//d1agz031tafz8n.cloudfront.net/thedaywefightback.js/widget.min.js";var t=document.getElementsByTagName("script")[0];t.parentNode.insertBefore(e,t)})()
-  </script>
-<!--<![endif]-->

app/views/layouts/application.html.slim

@@ -22,4 +22,3 @@ html[lang="en"]
     = render 'shared/flash'
     .main = content_for?(:content) ? yield(:content) : yield
     = render 'layouts/footer'
-    = render 'layouts/twfb'