title: Check if column in dataframe is missing values
body: <p>I have am column full of state names. 
  I know how to iterate down through it, but I don't know what syntax to use to have it check for empty values as it goes. tried "isnull()" but that seems to be the wrong approach. Anyone know a way?</p>
  
  <p>was thinking something like:</p>
  
  <pre><code>for state_name in datFrame.state_name:
      if datFrame.state_name.isnull():
          print ('no name value' + other values from row)
      else:
          print(row is good.)
  
  df.head():
   state_name state_ab            city zip_code
  0    Alabama       AL       Chickasaw    36611
  1    Alabama       AL      Louisville    36048
  2    Alabama       AL      Columbiana    35051
  3    Alabama       AL         Satsuma    36572
  4    Alabama       AL  Dauphin Island    36528
  
  
  to_dict():
  {'state_name': {0: 'Alabama',
    1: 'Alabama',
    2: 'Alabama',
    3: 'Alabama',
    4: 'Alabama'},
   'state_ab': {0: 'AL', 1: 'AL', 2: 'AL', 3: 'AL', 4: 'AL'},
   'city': {0: 'Chickasaw',
    1: 'Louisville',
    2: 'Columbiana',
    3: 'Satsuma',
    4: 'Dauphin Island'},
   'zip_code': {0: '36611', 1: '36048', 2: '35051', 3: '36572', 4: '36528'}}
  </code></pre>