Display all of arguments which are specified as otherButtonTitles

I found a minor problem at following methods which are in category extension class for UIAlertView.
 * ``` + (void)showAlertViewForTaskWithErrorOnCompletion:(NSURLSessionTask *)task
                                         delegate:(id)delegate
                                cancelButtonTitle:(NSString *)cancelButtonTitle
                                otherButtonTitles:(NSString *)otherButtonTitle, ... ```
 * ``` + (void)showAlertViewForRequestOperationWithErrorOnCompletion:(AFURLConnectionOperation *)operation
                                                     delegate:(id)delegate
                                            cancelButtonTitle:(NSString *)cancelButtonTitle
                                            otherButtonTitles:(NSString *)otherButtonTitle, ...```  

For instance, if the ```otherButtonTitles, ...``` argument is set to ```@"button1", @"button2", @"button3", nil``` , the alertView will be displayed like this.  

![UIAlertView (set to button1, button2, button3 as otherButtonTitle)](https://cloud.githubusercontent.com/assets/5053240/5236802/07d1c9d8-7894-11e4-9aba-0f90f579d2e6.png)

However,  these methods display only first argument (``` @"button1" ```).
The reason of this, these method deliver the argument which is recieved  as "```otherButtonTitles```" to UIAlertView's function.
Variable arguments  cannot be delivered  to another method.
So I attempt to separate this for each argument by using ```va_start, va_arg, va_end``` API and set these separated argument to title for ```UIAlertView```.
Hope you like this proposal :smile: