Include `href` or `to_param` when constructing URLs client side

One nice feature that Rails provides is easy changes to URL generation
(assuming the param starts with the ID). All you have to do is

```ruby
def to_param
  [id, name].to_param
end
```

and everything "Just Works". This is lost, however, if you're manually
constructing URLs on the client side. This is avoided, if as a general
rule of thumb, we let the server decide how to construct the URLs, and
pass that information along.
@sgrif I'm guessing the intent here is that, by default, AM::S defines `to_param` itself (returning `id`) instead of relying on `to_param` being defined on `object`? If that's the case, depending on the intent of AM::S, maybe a PR to that repo changing/fixing the behavior of `to_param` there makes more sense?