Support return instance

[JayPar]

Hi, this is great library, all of my projects are using this alert view!
Can we have return instance so that we can set the alert's property ?

MTBlockAlertView* alertView = [MTBlockAlertView showWithTitle ... ];

UITextField *username = [alertView textFieldAtIndex:0];
username.placeholder = @"Enter user name";
...

Many thanks!

[pwightman]

Glad you're finding it useful! If you make a pull request with the change, I'll happily merge it in, but it'll be a bit before I'll be able to do it myself unfortunately, sorry!