title: df.to_dict() only get one row of original dataframe (df)
body: <p>I have the following dataframe:</p>
  
  <p>Note: date is the index</p>
  
  <pre><code>city    morning afternoon   evening midnight
  date                    
  2014-05-01  YVR 2.32    4.26    -4.87   6.58
  2014-05-01  YYZ 24.78   2.90    -50.55  6.64
  2014-05-01  DFW 24.78   2.90    -50.55  6.64
  2014-05-01  PDX 2.40    4.06    -4.06   6.54
  2014-05-01  SFO 30.35   9.96    64.24   6.66
  </code></pre>
  
  <p>I try to save this df to a dict by df.to_dict() but I only get one row:</p>
  
  <pre><code>df.to_dict():
  
  {'city': {Timestamp('2014-05-01 00:00:00'): 'SFO'},
   'morning': {Timestamp('2014-05-01 00:00:00'): 9.9600000000000009},
   'afternoon': {Timestamp('2014-05-01 00:00:00'): 6.6600000000000001},
   'evening': {Timestamp('2014-05-01 00:00:00'): 30.350000000000001},
   'midnight': {Timestamp('2014-05-01 00:00:00'): 64.239999999999995}}
  </code></pre>
  
  <p>Shouldn't the entire dataframe be output in the dict? </p>