Support pagination

[WofloW]

reuse the keystone code to support pagination in restful-keystone

[WofloW]

@htor I have fixed jshint and jscs errors. But I have no idea how to solve the test error.
The first parameter of list methods is fx.model in test.

var query = fx.model.find(filter)
query.count() is not a function
query.find() is not a function

But in keystone those are existed.