Added tooltip for cloudwatch datasource

public/app/plugins/datasource/cloudwatch/partials/config.html

@@ -4,7 +4,7 @@
 <div class="tight-form last">
   <ul class="tight-form-list">
     <li class="tight-form-item" style="width: 160px">
-      Default Region
+      Default Region<tip>Specify the region, such as for US West (Oregon) use ` us-west-2 ` as the region.</tip>
     </li>
     <li>
       <input type="text" class="tight-form-input input-xlarge" ng-model='current.jsonData.defaultRegion' placeholder="" required></input>