This rule flags functions where the only thing they do is call their
super function and therefore could be omitted. For example:
```swift
override func foo() {
super.foo()
}
```
This can get pretty complex since there are a lot of slight variations
the subclasses' functions can call the superclasses' functions with, but
this covers many of the cases. Ideally this would handle variable
overrides too but it doesn't currently.
