Tooltip: Replace offset property with inline my+offset to make it easier

to override the offset. Fixes the odd offset in the video player demo.
Also doesn't need units.

Author: jzaefferer

demos/tooltip/video-player.html

@@ -32,7 +32,7 @@
 		$(".demo").tooltip({
 			position: {
 				my: "center top",
-				at: "center bottom+5px"
+				at: "center bottom+5",
 			},
 			show: {
 				duration: "fast"

ui/jquery.ui.tooltip.js

@@ -24,9 +24,8 @@ $.widget("ui.tooltip", {
 			return $( this ).attr( "title" );
 		},
 		position: {
-			my: "left center",
-			at: "right center",
-			offset: "15 0"
+			my: "left+15 center",
+			at: "right center"
 		}
 	},
 	_create: function() {