title: Array data appears as undefined?
body: <p>I have an array declared as so:</p>
  
  <pre><code>$scope.test=['blah', 'blah2'];
  </code></pre>
  
  <p>And I wanted to use ng-grid as a test to merely display the data. I did the following:</p>
  
  <pre><code>$scope.sourceGridOptionsApprovers = {
      plugins: [gridLayoutPlugin],
      data : 'test',
      columnDefs: [
          {field: 'test', displayName: 'Approvers', width:'35%',
              cellFilter: 'stringArrayFilter'}
      ]
  };
  </code></pre>
  
  <p>I wanted to filter the array so I could display the contents of test into one of my columns in ng-grid. I appended the following to my angular controller:</p>
  
  <pre><code>.filter('stringArrayFilter', function(){
          return function(myArray) {
              //console.log(myArray);
              return myArray.join(', ');
          };
      });
  </code></pre>
  
  <p>But when I try to display the contents of the array after I filter it, everything shows up as undefined, and I'm thinking it may be the way I passed in the array into the filter, but I'm not entirely sure. Any help would be appreciated.</p>
  
  <p>Here is a plunkr of my example: <a href="http://plnkr.co/edit/Ba7hoGFhI7cWWaD3itZx?p=preview" rel="nofollow">http://plnkr.co/edit/Ba7hoGFhI7cWWaD3itZx?p=preview</a></p>