shoes/shoes4 — pull request #615 by PragTob (2014-03-22 16:00:30+00:00)
Title: explicit delegation in Widget to app instead of method_missing

This is a follow up to #608

It's a bit more complicated with widgets... I included a comment about why - open for different solution strategies:

```ruby
# we set app 2 times because widgets execute most of their code
# straight in initialize. I dunno if there is a good way of setting
# an @app instance variable before initialize is executed. We could
# hand it over in #initialize but that would break the interface
# and people would have to set it themselves or make sure to call
# super so for not it's like this.
# Setting the ref on the instance is important as we might have
# instances of the same widget in different Shoes::Apps so each one
# needs to save the reference to the one it was started with
```