When a render view is closed, it's not guarrenteed that all objects'
weak callback would be called. So we must clean up all objects manually
after the render view gets closed.
Basic usage is:
remote = require 'remote'
Window = remote.require 'window'
w = new Window { width: 800, height: 600 }
Still need to do:
* Beter support for Array type.
* Remote objects should cheat devtools.
* Support cross-process callbacks.
