add more post data
subset of posts

in waitOn
        we subscribe to subset of data

in data:
        we specify the data context, so that client can re-control the
        data return from server
RouteController

RouteController is a tidy way to DRY
I need to figure it out: "this.route.path", why not "this.path"
and

the reason why nextPath in data:

in data, we define a "nextPath", named context, so we can use "nextPath"
rather than "this" in template, so there's no need to define a "nextPath"
helper.
I don't know things behind the scenes, but it's really easy to add
Should figure out "this" in router