Refactor aria JS to not be repetitive

[ashleykolodziej]

The JS around aria-labels is a little repetitive - it probably could be rethought to more easily set aria-labels correctly, as well as provide a framework for setting common aria labels on different types of functionality, like toggle, sliding panel, etc. Needs some thought though.

[ashleykolodziej]

In particular these two blocks are really similar:

https://github.com/bu-ist/responsive-foundation/blob/develop/js-dev/toggle.js#L18-L24
https://github.com/bu-ist/responsive-foundation/blob/develop/js-dev/toggle.js#L40-L47

It would be cool to think about how to allow child theme devs to access this type of JS so when we write custom JS for toggles or UI like on http://www.bu.edu/com/pathfinder/, we don't have to rewrite this function every time and a dev can just say "this should do the aria thing" as a long term goal. Short term, maybe there is a way to write a function that generalizes this a little more.