sensu: added input tooltip to source property

pkg/services/alerting/notifiers/sensu.go

@@ -26,7 +26,7 @@ func init() {
       </div>
       <div class="gf-form">
         <span class="gf-form-label width-10">Source</span>
-        <input type="text" class="gf-form-input max-width-14" ng-model="ctrl.model.settings.source"></input>
+        <input type="text" class="gf-form-input max-width-14" ng-model="ctrl.model.settings.source" bs-tooltip="'If emtpy rule id will be used'" data-placement="right"></input>
       </div>
       <div class="gf-form">
         <span class="gf-form-label width-10">Handler</span>