Month and year header dropdowns do not have labels associated

Related to but not mentioned in https://bugs.jqueryui.com/ticket/9627

To be friendly to screenreaders, the month and year header dropdowns should have labels associated with them. For formatting, the labels can actually be positioned offscreen if they cause too much clutter for sighted readers. See http://webaim.org/techniques/css/invisiblecontent/

I posted an issue on StackOverflow with an attempted workaround and it's quite painful compared to inserting two labels in the datepicker itself. (http://stackoverflow.com/questions/36779100/how-can-i-add-jaws-compatible-html-form-labels-to-month-and-day-dropdowns-in-jqu)