title: Pygsheets update_cells() not working
body: <p>I am trying to update a range of 3 cells horizontally using pygsheets but I am having some issues</p>
  
  <p>The Error:</p>
  
  <pre><code>Traceback (most recent call last):
    File "C:\Users\Art\Desktop\Python\Plain\General_testing.py", line 12, in &lt;module&gt;
      wks.update_cells('I{0}:K{0}'.format(rows),[output['Name'], output['Age'], output['State']])
    File "C:\Users\Art\AppData\Local\Programs\Python\Python36\lib\site-packages\pygsheets\worksheet.py", line 431, in update_cells
      self.client.sh_update_range(self.spreadsheet.id, body, self.spreadsheet.batch_mode, parse=parse)
    File "C:\Users\Art\AppData\Local\Programs\Python\Python36\lib\site-packages\pygsheets\client.py", line 352, in sh_update_range
      self._execute_request(spreadsheet_id, final_request, batch)
    File "C:\Users\Art\AppData\Local\Programs\Python\Python36\lib\site-packages\pygsheets\client.py", line 418, in _execute_request
      response = request.execute()
    File "C:\Users\Art\AppData\Local\Programs\Python\Python36\lib\site-packages\oauth2client\_helpers.py", line 133, in positional_wrapper
      return wrapped(*args, **kwargs)
    File "C:\Users\Art\AppData\Local\Programs\Python\Python36\lib\site-packages\googleapiclient\http.py", line 842, in execute
      raise HttpError(resp, content, uri=self.uri)
  googleapiclient.errors.HttpError: &lt;HttpError 400 when requesting https://sheets.googleapis.com/v4/spreadsheets/1P2FvtuOLWZGgVIp-D9ROeBqexXQt1eNv8tSxZdwGrlw/values/Sheet1%21I19%3AK19?valueInputOption=USER_ENTERED&amp;alt=json returned "Invalid value at 'data.values[0]' (type.googleapis.com/google.protobuf.ListValue), "Joe"
  Invalid value at 'data.values[1]' (type.googleapis.com/google.protobuf.ListValue), "19"
  Invalid value at 'data.values[2]' (type.googleapis.com/google.protobuf.ListValue), "NY""&gt;
  </code></pre>
  
  <p>Simplified version of my code that produces the same error:</p>
  
  <pre><code>import pygsheets
  
  gc = pygsheets.authorize(service_file='secret.json')
  sh = gc.open('TestSheet')
  wks = sh.sheet1
  
  row = 1
  output = {}
  output['Name'] = 'Joe'
  output['Age'] = '19'
  output['State'] = 'NY'
  wks.update_cells('I{0}:K{0}'.format(row),[output['Name'], output['Age'], output['State']])
  </code></pre>