message: Update sample_echo to respond to direct messages
diff: module.exports = function(controller) {
  - controller.hears('sample','message', async(bot, message) => {
  + controller.hears('sample','message,direct_message', async(bot, message) => {
  await bot.reply(message, 'I heard a sample message.');
  });
  - controller.on('message', async(bot, message) => {
  + controller.on('message,direct_message', async(bot, message) => {
  await bot.reply(message, `Echo: ${ message.text }`);
  });
  