title: Python: Adding values from multiple dictionaries and merging unique keys
body: <p>I have 2 dictionaries that share about 80% the same keys and the values are 2 element lists. I need to make a new dictionary out of the three that will contain all the keys, including the ones unique to each dictionary and I need the values of the same keys to be summed up.</p>
  
  <pre><code>    dict1 = {'Mike': [10,20], 'John': [12,34], 'Steve': [60,10]}
      dict2 = {'Mike': [15,10], 'John': [18,36]}
  </code></pre>
  
  <p>The new dictionary should look like this :</p>
  
  <pre><code>    dict3 = {'Mike': [25,30], 'John': [30,70], 'Steve': [60,10]}
  </code></pre>
  
  <p>Any idea how I should tackle this ?</p>