Changed regex for data attributes

The following regex in widgets.js should be extended from this /^data-[a-z]+$/ to this /^data-[a-z\\-]+$/

Currently it's only possible to add data attributes like "data-foo" but not like "data-foo-bar"

http://www.w3.org/TR/2010/WD-html5-20101019/elements.html#embedding-custom-non-visible-data-with-the-data-attributes