title: gridstack margin width not set -- items touch each other on each row
body: <p>I am using gridstack for the first time and I am having trouble with the horizontal margins.  Clearly there is something in my css that is making my items too wide.</p>
  
  <p>I see in the demos that gridstack.css has left and right set  at 10px each, and I am using that same default css.</p>
  
  <p>I have set gridstack up to use 6 columns as follows:</p>
  
  <pre><code>&lt;div id="container" class="grid-stack grid-stack-6"&gt; 
    &lt;div class="grid-stack-item"
      data-gs-x="0" data-gs-y="0"
      data-gs-width="3" data-gs-height="2"&gt;
          &lt;div class="grid-stack-item-content"&gt;
          &lt;i class="icon-lock-open pinDiv warning"&gt;&lt;/i&gt;
          &lt;i class="icon-cancel-circled"&gt;&lt;/i&gt;
          PRE MAP
    &lt;/div&gt;
   &lt;div class="grid-stack-item lockAspect"
      data-gs-x="3" data-gs-y="0"
      data-gs-width="3" data-gs-height="2"&gt;
          &lt;div class="grid-stack-item-content" style="background:pink;"&gt;
          &lt;i class="icon-lock pinDiv warning"&gt;&lt;/i&gt;
          &lt;i class="icon-cancel-circled"&gt;&lt;/i&gt;
          POST MAP
          &lt;/div&gt;
    &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>I am using the following options:</p>
  
  <pre><code>DEFAULT_GRIDSTACK_OPTIONS =  {
      cellHeight: 150,
      verticalMargin: 10,
      width: 6
  };
  </code></pre>
  
  <p>and I am including gridstack-extra as well as gridstack.css.</p>
  
  <p>Why do my items have no horizontal margin at all?</p>
  
  <p>thanks so much</p>