Add documentation for the ':wedge' style for arc.
Add missing ':center' style to arc.
Move adjustment for (left, top) if :center is set to a common routine.
Use new routine from arc, oval and rect
Initial commit of relative dimensions support

This will resolve issue #380. The Dimensions class needs an update to draw the
width and/or height from the parent, which now needs to be passed in to work
properly.

For the time being I've chosen to make it graceful if an object doesn't pass
the parent, but this might not be necessary once all the DSL elements properly
support the parent.
Modified DSL to support radio group attribute

Added tests and code to support :group for radio buttons at the DSL
(non-SWT) level.
resolved merge from master
Added a 'center' option to Dimension init method.
Support :center in init_with_hash
If center is true, adjusts @left and @top by half of @width and @height respectively.
Updated Rect, Arc and Oval to pass whether :center is set in their opts hash.
Updated Dimension, Arc, Rect and Oval specs.
Merge pull request #1 from PragTob/jasonrclark-relative_dimensions

Merge in master branch
Shared examples for dimensioning
Added basics of RadioGroup

Added starting structure of RadioGroup.
Refactored SelectionListener

Refactored SelectionListener to common base class.
Created separate Radio class

Made separate Radio class since it now has group functionality.
Added group attributes

Added group attributes and moved radio_groups to RadioGroup class.
Updates as per feedback:
* Changed Dimension initialize method to take an options hash as the last parameter
* Renamed adjust_for_center as adjust_for_left_top_as_center
* Pass through of options hash from Shoes::Arc, Shoes::Rect and Shoes::Oval
* Added shared example to common_methods.rb "left, top as center"
Added testing and refactored location or radio groups

Added testing for RadioGroup and Radio and moved all_groups to
RadioGroup.
Apply shared dimensions spec throughout DSL
Added additional Radio tests

Added radio tests for group=.
Modified bin/shoes script to run from everywhere

* it also uses bin/ruby-shoes so that the require/execute logic
  is not duplicated :-)
Potential fix for Shoes::CheckButton dimensions

Turns out that both Shoes::Button and Shoes::CheckButton derive from SwtButton, but
only Shoes::Button's DSL was being allowed to set widths appropriately here.
Now with a basic implementation of readlink -f for mac inside (so it works there)