added image file check for background images
Add App#gutter
Use reported size of scrollbar
Fix mock gutter
images not found does not raise error
now unfound images do not raise an error
Merge branch 'no-file-error' of github.com:presidentJFK/shoes4 into no-file-error
removed pry
Add #displace, with specs and sample
use def_delegators instead of method_missing for Shoes::URL

* we know all the methods we want to delegate in advance, so
  def_delegators communicates that better
* also it is (presumably) faster than walking down the method
  chain once already
* also it is less prone to errors... e.g. trying to delegate
  methods we do not want to delegate
Make setting the parent of a widget more understandable
Add displace methods to Dimensions
Merge pull request #608 from shoes/replace_method_missing

use def_delegators instead of method_missing for Shoes::URL
Merge with master. Hairy
Merge pull request #613 from shoes/no-file-error

Gracefully handle missing background images
Explicitly delegate missing methods to app from widgets

* App lookup is a bit more complicated as we need to have
  app available during initialization
* got rid of method_missing
Blacklist parent method to not delegate it to app
Use #update_position
Change #displace to #update_position in gui
Merge with master