title: pandas DataFrame to list of dicts using to_json()
body: <p>So, i'm reading a xlsx file with pandas, then parsing the datetime (excel's a float)</p>
  
  <p>Then I need to parse it into Json, and I'm running into some problems.</p>
  
  <p>STEP 1 (Before parsing with to_json())</p>
  
  <pre><code>df = pandas.read_excel('test.xlsx', names=['date', 'value', 'source'])
  df['date'] = pandas.to_datetime(df['date'], format='%b %d %Y.%f')
  print(df)
  </code></pre>
  
  <p>the return is </p>
  
  <pre><code>        date  value                            source
  0 2012-05-22      1              xxxxxxxxxxxxxxxxxxxx
  1 2012-05-25      1                     xxxxxxxxxxxxx
  2 2012-05-30      1  xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
  3 2012-06-01      1                        xxxxxxxxxx
  4 2012-06-08      1                 xxxxxxxxxxxxxxxxx
  </code></pre>
  
  <p>Everything seems fine, then I got o to_json</p>
  
  <pre><code>payload = df.to_json()
  </code></pre>
  
  <p>And the return is </p>
  
  <pre><code>{"date":{"0":1337644800000,"1":1337904000000,"2":1338336000000,"3":1338508800000,"4":1339113600000},"value":{"0":1,"1":1,"2":1,"3":1,"4":1},"source":{"0":"xxxxxxxxxxxxxxx","1":"xxxxxxxxxx","2":"xxxxxxxxxxx","3":"xxxxxxxxxxxxxxxx","4":"xxxxxxxxxxxxxxx"}}
  </code></pre>
  
  <p>So what am I doing wrong? Am I missing args on to_json()? Halp pls :c</p>
  
  <p>I needed it to be like this: </p>
  
  <pre><code>[{"date":"2012-05-22","value":1,"source":"xxxxxxxxxxxxxxxxxxxx"},
  {"date":"2012-05-25","value":1,"source":"xxxxxxxxxxxxxxxxxxxx"},
  {"date":"2012-05-30","value":1,"source":"xxxxxxxxxxxxxxxxxxxxx"},
  {"date":"2012-06-01","value":1,"source":"xxxxxxxxxxxxxxxxxxxx"},
  {"date":"2012-06-08","value":1,"source":"xxxxxxxxxxxxxxxxxxxxxx"}]
  </code></pre>