title: change color of tooltip arrow of ui.bootrap (plunker attached)
body: <p>here is the plunker code. 
  <a href="http://plnkr.co/edit/C1khFJqTUutDaK9ad7ud?p=preview" rel="noreferrer">http://plnkr.co/edit/C1khFJqTUutDaK9ad7ud?p=preview</a> </p>
  
  <p>I need to change the tooltip arrow. the position of the tooltips in the example is top, bottom and left. </p>
  
  <p>Can someone let me know how to style these tooltips. I need to color the tooltip arrow differently for different locations of tooltip.</p>
  
  <p>for e.g</p>
  
  <pre><code>tooltip at top-&gt; arrow color should be red
  tooltip at bottom-&gt; arrow color green
  tooltip at left-&gt; arrow color yellow
  </code></pre>
  
  <p>Can someone let me know how to get those classes and apply the color to these tooltips. </p>
  
  <p>Here is the code</p>
  
  <p>HTML</p>
  
  <pre><code>&lt;div ng-controller="TooltipDemoCtrl"&gt;
  &lt;br&gt;&lt;br&gt;&lt;br&gt;
    &lt;div ng-class="{'has-error' : !inputModel}"&gt;
      &lt;input type="text" ng-model="inputModel" class="test"
        uib-tooltip="Tooltip TBD"
        tooltip-placement="top"
        tooltip-trigger="mouseenter"
        tooltip-enable="!inputModel" /&gt;
    &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>CSS</p>
  
  <pre><code>.tooltip .tooltip-inner {
              color: white;
              background-color: blue;
              border-radius:5px;
  }
  
  .tooltip .tooltip-arrow { 
            //cant get the class for the arrow
  
  }
  </code></pre>