Use string instead of ol.proj.Units enum in examples

examples/zoomify.js

@@ -4,7 +4,6 @@ goog.require('ol.View2D');
 goog.require('ol.layer.Tile');
 goog.require('ol.proj');
 goog.require('ol.proj.Projection');
-goog.require('ol.proj.Units');
 goog.require('ol.source.Zoomify');
 
 // This server does not support CORS, and so is incompatible with WebGL.
@@ -26,7 +25,7 @@ var imgCenter = [imgWidth / 2, - imgHeight / 2];
 // can use to properly display the layer.
 var proj = new ol.proj.Projection({
   code: 'ZOOMIFY',
-  units: ol.proj.Units.PIXELS,
+  units: 'pixels',
   extent: [0, 0, imgWidth, imgHeight]
 });