Very basic Radio input rendering started.
Add support for complex input type format.
Add checked + disabled support to radio buttons.
Add support for custom labels.

You can both disable and customize all of the labels with additional
properties.
Add tests for usage of radioContainer.
Add empty option support.

Add the empty option that FormHelper currently supports.
Move files to match 3.0 directory moves.
Cleanup based on review comments.
Add a test for using an Collection for options.

Traversable/Collection instances should work for options.
Add doc blocks.
Fix coding standards issue.
Extract a protected method.

If anyone wants to subclass this, having a separate method will be nice.
Make it easy to put inputs *inside* label elements.

This is a frequently requested feature that is much easier to implement
now. Add it so it is easy to integrate bootstrap & older versions of
foundation.
Merge pull request #2640 from markstory/3.0-radio-widget

3.0 - Create radio widget