Using new duck
Mostly collision detection stuff

Also made sure FloatyElements only allow one instance per ID (facilitates
easy resetting of elements, plus obyes HTML validation)
Added basic obstacles

Also made .elem a recursive part of FloatyElement, but that's not being
used yet. Part of this was changing how init functions happen to put a
post_init hook into FloatyElement.
Merge branch 'master' into daniel

Conflicts:
	js/FloatyDuck.js
	style.css
Merge pull request #17 from floatyduck/daniel

Merge in daniel