title: DynamoDB update Item multi action
body: <p>I am trying to update an item in DynamoDB table:</p>
  
  <pre><code>var params = {
          TableName: 'User',
      Key: {
          id: 'b6cc8100-74e4-11e6-8e52-bbcb90cbdd26',
      },
      UpdateExpression: 'ADD past_visits :inc, past_chats :inc',
      ExpressionAttributeValues: {
          ':inc': 1
      },
          ReturnValues: 'ALL_NEW'
      };
      docClient.update(params, function(err, data) {
          if (err) ppJson(err); // an error occurred
          else ppJson(data); // successful response
      });        
  </code></pre>
  
  <p>It's working. But I want to set some more value (reset_time = :value') like this:</p>
  
  <pre><code>var params = {
          TableName: 'User',
      Key: {
          id: 'b6cc8100-74e4-11e6-8e52-bbcb90cbdd26',
      },
      UpdateExpression: 'ADD past_visits :inc, past_chats :inc, SET reset_time = :value',
      ExpressionAttributeValues: {
          ':inc': 1,
          ':value': 0
      },
          ReturnValues: 'ALL_NEW'
      };
      docClient.update(params, function(err, data) {
          if (err) ppJson(err); // an error occurred
          else ppJson(data); // successful response
      });
  </code></pre>
  
  <p>Can DynamoDb support multi action in one query ?</p>