Add more window globals and shims in task shell

This allows jQuery to be successfully loaded from a web worker
since it does not have a document or window object by default.

Previously it would log about missing methods and properties.

Closes #228

src/stdlib/task.coffee

@@ -17,7 +17,10 @@ class Task
 
   startWorker: ->
     @callWorkerMethod 'start'
-      resourcePath: window.resourcePath
+      globals:
+        resourcePath: window.resourcePath
+        navigator:
+          userAgent: navigator.userAgent
       requirePath: require.getPath('require')
       handlerPath: @path