title: TaxJar method is not returning anything
body: <p>I am using TaxJar integration in one of my projects to calculate the tax for an order. I have integrated TaxJar like this:</p>
  
  <pre><code>    $client = TaxJar\Client::withApiKey("8516090bdbb97d99632daa2acaf910aa30");
  
      $order_taxes = $client-&gt;taxForOrder([
          'from_country' =&gt; 'US',
          'from_zip' =&gt; '07001',
          'from_state' =&gt; 'NJ',
          'to_country' =&gt; 'US',
          'to_zip' =&gt; '07446',
          'to_state' =&gt; 'NJ',
          'amount' =&gt; 16.50,
          'shipping' =&gt; 1.5,
          'line_items' =&gt; [
              [
                  'quantity' =&gt; 1,
                  'unit_price' =&gt; 15.0,
                  'product_tax_code' =&gt; 31000
              ]
          ]
      ]);
  </code></pre>
  
  <p>When I do <code>var_dump($client)</code>, it shows all the details of the TaxJar dependencies which are included, but when I do <code>var_dump($order_taxes)</code> it shows nothing.</p>
  
  <p>What should I do to get this work?</p>