knockout/knockout — pull request #1664 by smilce (2014-12-29 06:17:24+00:00)
Title: overwrite toString method of observable

overwrite toString method of observable,to make the getting obj's value more like a variable,following is code
```javascript
this.selectedIndex = ko.observable(-1);
console.log(this.selectedIndex());//before overwriting
console.log(this.selectedIndex(), this.selectedIndex); // after overwriting