Accordion module wrapper

[caitp]

I don't necessarily feel like it's needed to make big complicated templates for the contents of an accordion. However, if people think this is useful, I'm not necessarily against it. I just think it's a much simpler world where it's not necessary to worry about it.

Currently, the Accordion module supports the following:

• Specify the four accordion settings defined in the spec via attributes
• Handle accordion events as AngularJS expressions with a local variable containing the active element (according to the docs)

Things that are missing which might be useful:

• Debug options -- I really want to make debug configuration stuff a global service, where each module can find out if it's required to output debug info by checking its position within an array or string or something. This seems like a sane way to do this. Reason being, it seems unlikely to need to set up debug info on an individual instance by instance basis. Maybe I'm wrong about this use case, though.
• Specify options via global configuration -- This is not a terribly difficult thing to do, so why not.

So generally I'm pretty happy with this one so far, and I'm probably going to move onto the next problem before dealing with these other issues.