Add annotate_rb gem and annotate all models

app/models/completion.rb

@@ -1,3 +1,27 @@
+# == Schema Information
+#
+# Table name: completions
+#
+#  id            :integer          not null, primary key
+#  time_seconds  :integer
+#  created_at    :datetime         not null
+#  updated_at    :datetime         not null
+#  contest_id    :integer          not null
+#  contestant_id :integer          not null
+#  puzzle_id     :integer          not null
+#
+# Indexes
+#
+#  index_completions_on_contest_id     (contest_id)
+#  index_completions_on_contestant_id  (contestant_id)
+#  index_completions_on_puzzle_id      (puzzle_id)
+#
+# Foreign Keys
+#
+#  contest_id     (contest_id => contests.id)
+#  contestant_id  (contestant_id => contestants.id)
+#  puzzle_id      (puzzle_id => puzzles.id)
+#
 class Completion < ApplicationRecord
   belongs_to :contest
   belongs_to :contestant