fix(Header): Use IE9 condcom to fix header sizing

IE9 wasn't aligning the column headers properly. Not really worried about
a permanent pretty fix here given IE9's age. This just hacks around the
problem.

Thanks to @chuge for the CSS.

Fixes #3854

src/templates/ui-grid/ui-grid.html

@@ -25,6 +25,24 @@
     {{ grid.customStyles }}
   </style>
 
+
+  <!--[if IE 9]>
+  <style>
+    .ui-grid-header-cell-wrapper {
+      display: block;
+    }
+
+    .ui-grid-header-cell-row {
+      display: block;
+    }
+
+    .ui-grid-header-cell {
+      display: block;
+      float: left;
+    }
+  </style>
+  <![endif]-->
+
   <div class="ui-grid-contents-wrapper">
     <div ui-grid-menu-button ng-if="grid.options.enableGridMenu"></div>