Async, Background, and Local Dispatchers support

[JoshuaBrest]

I think we should add the following features to make development easier:

• Async
  • Maybe you need to call async functions
  • Could be done by calling a background task to modify the view later instead of in the did_load
• Background
  • Maybe a background task might be useful for like setInterval
• Local Dispatcher
  • So that instead of adding complicated logic in App, you can do it in the local view impl