Fix replacing urls in css handler

Author: s0ph1e

lib/file-handlers/css.js

@@ -17,7 +17,7 @@ function loadCss (context, resource) {
 
 		return context.loadResource(cssResource).then(function handleLoadedSource (loadedResource) {
 			var relativePath = utils.getRelativePath(filename, loadedResource.getFilename());
-			text = text.replace(new RegExp(cssUrl, 'g'), relativePath);
+			text = text.replace(cssUrl, relativePath);
 			return Promise.resolve();
 		});
 	});