Add maxHeight property to allow scrolling message

Adds a 'maxHeight' property to FUIAlertView that allows for extraordinarily long text- similarly to how UIAlertView handles long text (instead of simply showing a gigantic alert box!). The feature can be enabled with something along the lines of

    alertView.maxHeight=300;

before showing the alert. Using the above value in the included example (with a modified message, of course) produces the following:

![ios simulator screen shot oct 14 2013 8 09 51 pm](https://f.cloud.github.com/assets/3643764/1331112/518d67e4-3547-11e3-9dc8-4096ce2182c7.png)