Embed segue for iOS 6 & 7 (using constraints to pin edges of subview to container view)

EmbedSegue.h

//
//  EmbedSegue.h
//  Created by Stephanie Sharp on 20/02/14.
//

#import <UIKit/UIKit.h>

@interface EmbedSegue : UIStoryboardSegue

@property (nonatomic) UIView *containerView;
@property (nonatomic) CATransition *transition;

@end

EmbedSegue.m

//
//  EmbedSegue.m
//  Created by Stephanie Sharp on 20/02/14.
//

#import "EmbedSegue.h"

@implementation EmbedSegue

- (void)perform
{
    if (self.transition) {
        [self.containerView.layer addAnimation:self.transition forKey:kCATransition];
    }

    UIView * subview = [self.destinationViewController view];
    subview.translatesAutoresizingMaskIntoConstraints = NO;

    [self.sourceViewController addChildViewController:self.destinationViewController];
    [self.containerView addSubview:subview];
    [self.destinationViewController didMoveToParentViewController:self.sourceViewController];

    NSDictionary * views = NSDictionaryOfVariableBindings(subview);
    [self.containerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[subview]|"
                                                                               options:0
                                                                               metrics:nil
                                                                                 views:views]];
    [self.containerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[subview]|"
                                                                               options:0
                                                                               metrics:nil
                                                                                 views:views]];
}

- (UIView *)containerView
{
    if (!_containerView) {
        _containerView = [self.sourceViewController view];
    }
    return _containerView;
}

@end

Could this gist be released under MIT or Apache 2?