method for filter property starts with the passed value

Hi,

I have added a method which return the array having property starts with the passed value.

For Ex:

var myArray = [
 Ember.Object.create(firstName: "abcde", lastName: "fghij"),
 Ember.Object.create(firstName: "ab678878", lastName: "djsfhk"),
 Ember.Object.create(firstName: "abbgd",lastName: "cxgd"),
 Ember.Object.create(firstName: "dsgf",lastName: "sdfs")
]

Ember.Object.create(myArray).filterPropertyStartWith("firstname","ab")

will return array of 3 items