Rewrite hit test method

Rewrite hit test method, so users can hit components below the empty view.

public text color property

user can set empty message's text color.

Add refresh button

Add a refresh button in empty view. You can do something in the clickClosure.

Add more examples.

Add pull to refresh in empty view.

Fix an error.

Delete default images. Now developer must provide an image for the empty view.

Fix an error.

Fix an error.

Add empty view for your views.

1. Add empty view for your views.
2. Support custom empty tip messages and images.