Instead of using spoiler boolean and spoiler_text, simply check for non-blank spoiler_text

Federate spoiler_text using warning attribute on <content /> instead of a <category term="spoiler" />
Clean up schema file from accidental development migrations

db/migrate/20170112041538_add_spoiler_to_statuses.rb

@@ -1,5 +0,0 @@
-class AddSpoilerToStatuses < ActiveRecord::Migration[5.0]
-  def change
-    add_column :statuses, :spoiler, :boolean, default: false
-  end
-end