title: reduce is not giving right sum
body: <p>My Object <code>groupBy.Food</code> looks like  </p>
  
  <pre><code>[
  Object
  amount: "15.0"
  category: Object
  debit: true
  __proto__: Object
  , 
  Object
  amount: "10.0"
  category: Object
  debit: true
  __proto__: Object
  , 
  Object
  amount: "11.1"
  category: Object
  debit: true
  __proto__: Object
  ]
  </code></pre>
  
  <p>All I want is <code>sum</code> of amount in each object. I am using <a href="http://lodash.com/docs#reduce" rel="noreferrer">Lodash reduce</a> as </p>
  
  <pre><code>var s = _.reduce(groupBy.Food, function(s, entry){
     return s + parseFloat(entry.amount);
  });
  </code></pre>
  
  <p>When I see value of <code>s</code> I get</p>
  
  <pre><code>s
  "[object Object]1011.1"
  </code></pre>
  
  <p>What is that I am not doing right here?</p>