Support widgets which define items either as a property or as a method.
This provides compatibility with SelectWidget in z3c.form v3.0.
Fixed setting or unsetting of disabled attribute on select tag for jquery 1.6+ compatibility
Add changelog entry
Merge pull request #2 from damilgra/master

Add compatibility for z3c.form 3.0 and jquery 1.6+, and therefore Plone 4.3+