Reverse method on event readers.

Related to #87.
Hm, I've noticed that... But that might be only an IntelliSense issue. The compiler shouldn't favor the extension method.

Right now, I did a test and changed the `Reverse` method to return `IEnumerable<T>` and debugged this:

```c#
var actual = sut.Reverse();
```

And the debugger stepped into the correct method, the `IEnumerbale<T> FifoEvents<T>.Reverse()`.