set default values for approved and answered

db/migrate/20161013162214_create_access_requests.rb

@@ -2,8 +2,8 @@ class CreateAccessRequests < ActiveRecord::Migration[5.0]
   def change
     create_table :access_requests do |t|
       t.references :user, foreign_key: true
-      t.boolean :approved
-      t.boolean :answered
+      t.boolean :approved, default: false
+      t.boolean :answered, default: false
       t.references :map, foreign_key: true
 
       t.timestamps