adds Poll::Answer model for web users

PartialResults is kept for booth results

db/migrate/20170125112017_create_poll_answers.rb

@@ -0,0 +1,15 @@
+class CreatePollAnswers < ActiveRecord::Migration
+  def change
+    create_table :poll_answers do |t|
+      t.integer :question_id
+      t.integer :author_id
+      t.string :answer
+
+      t.timestamps
+    end
+
+    add_index :poll_answers, :question_id
+    add_index :poll_answers, :author_id
+    add_index :poll_answers, [:question_id, :answer]
+  end
+end