PhotoEditorViewController leaking memory via retain cycle

[jonchui]

When you push the PhotoEditorViewController and finish, you can see in the Xcode memory guage that a huge amount of heap memory isn't getting released. Most likely due to the image.

Here i've edited 5 different photos, going back to the main screen each time (which should reset the heap) . You can see every time the heap increases but does not go down after popping:

[jonchui]

After fixing those initial leaks (cause by retain cycles w/ non-weak delegates), i found some more:

Here's a gif of my run:
http://recordit.co/UISvPsprVd.gif

[jonchui]

FYI: i opened PR #42 that fixes it ;)