change(): updated placeholder text in data source edit view

public/app/features/plugins/partials/ds_http_settings.html

@@ -5,7 +5,7 @@
 
 	<div class="gf-form">
 		<span class="gf-form-label width-7">Url</span>
-		<input class="gf-form-input max-width-21" type="text" ng-model='current.url' placeholder="http://my.server.com:8080" ng-pattern="/^(ftp|http|https):\/\/(\w+:{0,1}\w*@)?(\S+)(:[0-9]+)?(\/|\/([\w#!:.?+=&%@!\-\/]))?$/" required></input>
+		<input class="gf-form-input max-width-21" type="text" ng-model='current.url' placeholder="for example: http://localhost:8080" ng-pattern="/^(ftp|http|https):\/\/(\w+:{0,1}\w*@)?(\S+)(:[0-9]+)?(\/|\/([\w#!:.?+=&%@!\-\/]))?$/" required></input>
 
 		<info-popover>
 			<p>Specify a complete HTTP url (http://your_server:8080)</p>