title: Increasing _MAX_ROWS_PER_REQUEST in google-bigquery python api
body: <p>I have been using the google-bigquery python api and in the bigquery_client.py file I see there is a global _MAX_ROWS_PER_REQUEST = 1000000.  I have been querying some genomics data and expect responses larger than 1000000 rows.  I tried to increase this variable but I seem to get some strange results.  An example...</p>
  
  <pre><code>import bq
  .
  .
  .
  q = """ &lt;my query&gt; """
  q_result = client.Query(q,destination_table="blah:blah.A")
  table_ref = q_result['configuration']['query']['destinationTable']
  fields, data = client.ReadSchemaAndRows(table_ref)
  print len(data) 
  </code></pre>
  
  <p>The length returned is 1050000 which is a list of rows and is less than the exported table blah:blah.A which is ~2.7 million rows in BQ (the correct length).</p>
  
  <p>I then increased _MAX_ROWS_PER_REQUEST = 10000000 and reran the above and got 10015439 as the length!</p>