Correction time regex in the add Methods

Archive: http://ajax.aspnetcdn.com/ajax/jquery.validate/1.8.1/additional-methods.js

The regex was this way above:

``` javascript
/^([01][0-9])|(2[0123]):([0-5])([0-9])$/
```

If you enter "12" for example, it returns true.

I propose this new regex:

``` javascript
/^([0-1][0-9]|[2][0-3])(:([0-5][0-9])){1,2}$/
```
