A bugfix and a new feature

Hi, 

Here is 2 commits that I've made for my project needs: 
- 1 Bugfix about the container view height. To understand the bug, simply do this in the PSStackedViewExample AppDelegate, and launch the App in horizontal orientation: 
```
    // set root controller as stack controller
    ExampleMenuRootController *menuController = [[ExampleMenuRootController alloc] init];
    self.stackController = [[PSStackedViewController alloc] initWithRootViewController:menuController];

    ExampleViewController1 * vc = [[ExampleViewController1 alloc] init];
    [[self stackController] pushViewController:vc animated:NO];
```

- 1 new feature that allow overlapped VC to come back to front within a tap (like the old Twitter way). 

J.