Updated UIScrollView example in order to use scrollRectToVisible

With the previous example we encountered that scrollRectToVisible method was broken.
I added a tap gesture to every view to test it :)
This is fixed by adding a "content" UIView inside the scrollView where we will add everything we need (in this case randomly colored views).
Merge pull request #26 from lluisgerard/patch-1

Updated UIScrollView example in order to use scrollRectToVisible