title: Merged columns while exporting to .csv are not showing properly
body: <p>I am using <code>angular-ui-grid</code> version <code>v3.0.0-rc.22-e8fe073</code>. In a grid there are few merged columns and the column definition of merged column is as below:</p>
  
  <pre><code>mergedColumn :true, mergedColumnDisplayName :'Client Buy', name:'buy',field:'buy','displayName':'Amount',enableHiding: false
  </code></pre>
  
  <p>Below is the headertemplate being used:</p>
  
  <pre><code>$scope.sHeaderTemplate ='&lt;div class="ui-grid-header"&gt; \
                          &lt;div class="ui-grid-top-panel"&gt;\
                          &lt;div class="ui-grid-header-viewport"&gt;\
                          &lt;div class="ui-grid-header-canvas"&gt;\
                          &lt;div class="ui-grid-header-cell-wrapper" ng-style="colContainer.headerCellWrapperStyle()"&gt;\
                          &lt;div class="ui-grid-header-cell-row"&gt;\
                          &lt;div class="ui-grid-header-cell ui-grid-clearfix" ng-if="!col.grouping"\
                              ng-repeat="col in colContainer.renderedColumns track by col.uid"\
                           col="col" render-index="$index"  ng-class="{\'ui-grid-header-cell-merged\': col.colDef.mergedColumnDisplayName}" &gt;\
                           &lt;div  class="ui-grid-header-cell-merged-title"&gt;&amp;nbsp; {{col.colDef.mergedColumnDisplayName}} &lt;/div&gt; \
                          &lt;/div&gt;\
                          &lt;/div&gt;\
                          &lt;div class="ui-grid-header-cell-row"&gt;\
                          &lt;div class="ui-grid-header-cell ui-grid-clearfix" ng-if="!col.grouping"\
                              ng-repeat="col in colContainer.renderedColumns track by col.uid"\
                          ui-grid-header-cell col="col" render-index="$index"&gt;\
                          &lt;/div&gt;\
                          &lt;/div&gt;\
                          &lt;/div&gt;\
                          &lt;/div&gt;\
                          &lt;/div&gt;\
                          &lt;/div&gt;\
                          &lt;/div&gt;';
  </code></pre>
  
  <p>And in a grid <code>headerTemplate :  $scope.sHeaderTemplate</code>.</p>
  
  <p>Columns are displayed properly on a webpage. Please find below screenshot:</p>
  
  <p><a href="https://i.stack.imgur.com/9plvF.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/9plvF.png" alt="merged column in  a grid"></a></p>
  
  <p>Now, when I export this grid to .csv and open the .csv file in <code>MS Excel</code>, I am not getting merged columns.</p>
  
  <p><strong>How do I display merged columns from <code>angular-ui-grid</code> exported to csv in `MS Excel' ?</strong></p>