Add Support for <input type="datetime-local">

Initially, this started as an effort to support `<input type="datetime">`, but I learned that this has been replaced by `datetime-local` [in most cases](http://stackoverflow.com/questions/21263515/why-is-html5-input-type-datetime-removed-from-browsers-already-supporting-it).  This improves the styling for an input of this type.

Feedback appreciated.