Revert revokeObjectURL; simply attach objectURL

Reverts the change introduced by #16
Addresses #26

Author: Anand Thakker

example/main.js

@@ -1,7 +1,15 @@
 var work = require('../');
 
 var w = work(require('./worker.js'));
+
+var first = true;
 w.addEventListener('message', function (ev) {
+    if (first) {
+        // revoke the Object URL that was used to create this worker, so as
+        // not to leak it
+        URL.revokeObjectURL(w.objectURL);
+        first = false;
+    }
     console.log(ev.data);
 });
 

index.js

@@ -62,8 +62,6 @@ module.exports = function (fn, options) {
     if (options && options.bare) { return blob; }
     var workerUrl = URL.createObjectURL(blob);
     var worker = new Worker(workerUrl);
-    if (typeof URL.revokeObjectURL == "function") {
-      URL.revokeObjectURL(workerUrl);
-    }
+    worker.objectURL = workerUrl;
     return worker;
 };

readme.markdown

@@ -70,6 +70,12 @@ part. It is necessary for the main code to `require()` the worker code to fetch
 the module reference and load `modulePath`'s dependency graph into the bundle
 output.
 
+## Worker.objectURL
+
+The worker `w` returned by `webworkify` has the property `objectURL` attached.
+`w.objectURL` refers to the Object URL that was used to pass the module's source
+to the worker, and can be cleaned up using `URL.revokeObjectURL()`.  (See [example](https://github.com/substack/webworkify/blob/master/example/main.js))
+
 # install
 
 With [npm](https://npmjs.org) do: