Added Class util

First of all, congratulations for your great library. It's awesome! :)

I've added a class util that returns YES if all of the BZGForms contained in a View are in a valid state (otherwise NO). Now you can know with a single call if all the forms of a Controller are valid and load the next Controller/Whatever.

+ (BOOL)areValidAllFormsContainedInView:(UIView *)containerView;

I hope I find it as useful as I do!