build-in validators
added backbone.nested library
added backbone.relational library
creating a collection of model
get model at index
clone a model from a collection
get item from collection by id
added item to collection with add method
added model at specific position
adde multiple models
add comparator to a collection and can sort to sort the existing items

items added after the comparator will be sorted automatically
use overloaded comparator taking 2 models as input

-1 or any negative, 0, and 1 and and positive
simple filtering