v0.3.0

• added - (NSArray *)mas_updateConstraints:(void(^)(MASConstraintMaker *))block which will update existing constraints if possible, otherwise it will add them. This makes it easier to use Masonry within the UIView - (void)updateConstraints method which is the recommended place for adding/updating constraints by apple.
• Updated examples for iOS7, added a few new examples.
• Added -isEqual: and -hash to MASViewAttribute [CraigSiemens].