Responsive dropdown toggle

[nervetattoo]

This adds support for dropdown toggles going full-width on small screens, just like in the vanilla foundation.
It also moves mediaQueries to its own module, mm.foundation.mediaQueries, so it can be reused.
Fixes #98

[nervetattoo]

I also added some logic to make sure the dropdown does not overflow out of the screen on the right hand when the initiating button is placed far out.
Instead it aligns the dropdown with an 8px padding on the right hand side and forces the pip to be right-sided.

[circlingthesun]

👍

[jbrowning]

This is awesome, especially the separation of mediaQueries into a separate module. 😌

1. Can you please add some mediaQueries module docs for the demo page?
2. Are there any mediaQueries-related specs we should move into specs for the mediaQueries module?

[nervetattoo]

I didn't find any specs covering the mediaQueries part when I looked.
I've at least pushed a readme for the module now.

[jbrowning]

👍 thanks!