title: Python 2.7 CSV writer issue
body: <p>I have some Python code that lists pull requests in Github.  If I print the parsed json output to the console, I get the expected results, but when I output the parsed json to a csv file, I'm not getting the same results.  They are cut off after the sixth result (and that varies).  </p>
  
  <p>What I'm trying to do is overwrite the csv each time with the latest output.</p>
  
  <p>Also, I'm dealing with unicode output which I use unicodecsv for. I don't know if this is throwing the csv output off.</p>
  
  <p>I will list both instances of the relevant piece of code with the print statement and with the csv code.   </p>
  
  <p>Thanks for any help.</p>
  
  <pre><code>import sys
  import codecs
  sys.stdout = codecs.getwriter('utf8')(sys.stdout)
  sys.stderr = codecs.getwriter('utf8')(sys.stderr)
  import csv
  import unicodecsv
  
  for pr in result:
      data = pr.as_dict()
      changes = (gh.repository('my-repo', repo).pull_request(data['number'])).as_dict()   
      if changes['commits'] == 1 and changes['changed_files'] == 1:
          #keep print to console for testing purposes
          print "Login: " + changes['user']['login'] + '\n' + "Title: " + changes['title'] + '\n' + "Changed Files: " + str(changes['changed_files']) + '\n' + "Commits: " + str(changes['commits']) + '\n'
  </code></pre>
  
  <p>With csv:</p>
  
  <pre><code>import sys
  import codecs
  sys.stdout = codecs.getwriter('utf8')(sys.stdout)
  sys.stderr = codecs.getwriter('utf8')(sys.stderr)
  import csv
  import unicodecsv
  for pr in result:
      data = pr.as_dict()
      changes = (gh.repository('my-repo', repo).pull_request(data['number'])).as_dict()   
      if changes['commits'] == 1 and changes['changed_files'] == 1:
         with open('c:\pull.csv', 'r+') as f:
              csv_writer = unicodecsv.writer(f, encoding='utf-8')
              csv_writer.writerow(['Login', 'Title', 'Changed files', 'Commits'])
              for i in changes['user']['login'], changes['title'], str(changes['changed_files']), str(changes['commits']) :
                  csv_writer.writerow([changes['user']['login'], changes['title'],changes['changed_files'], changes['commits']])
  </code></pre>