Multiple device support

Fixes #54.

This provides basic support for multiple devices. It isn't styled correctly yet but in the interest of making testing easier, I thought that could wait for #85. There is some extra noise in this PR because I normalized some whitespace differences ([diff ignoring whitespace](https://github.com/jrconlin/wmf/pull/86/files?w=1)).

@pdehaan r?
You are so right. I fixed it but forgot to push it up. Thanks for catching that.