title: _.where with RegExp in object return empty lodash
body: <p>I am creating a filter for a JSON object to filter the result depending on the value of the field.</p>
  
  <p>if we have the object below:</p>
  
  <pre><code>var vo = [{
    "programName": "Tesco.com",
     "code": "FFCLUB10",
     "updateDate": "1424270164689"
  },
  {
     "id": 160320,
     "programId": 239597,
     "programName": "Panda Security UK"
  }];
  </code></pre>
  
  <p>Using the following code I want to filter the object and just have the one that programName starts with T:</p>
  
  <pre><code>Voucher = _.where(vo, { 'programName': new RegExp('^' + '[T]', 'i')});
  </code></pre>
  
  <p>However I have an empty object as a result, I am using the lodash module.
  Could you give me some lights on this?</p>
  
  <p>Thanks</p>