[Bindings] Adds hx.bindingHandler, fixes for IE8

The binding handler system in hx has been rewritten, introducing the
use of the html5 shiv (if available), automatic rewriting of custom
nodes
if necessary (e.g. a 'replacement' does not have to be specific in
binding
handler), and `hx.bindingHandler` method which is used to register all
binding handlers, which provides a place to create a binding handler
with dependencies without requiring hx.config hacks