30 raise nonstandard events

Fixes #30.

Now allowing raising of nonstandard events, with the syntax

```csharp
fake.Event += Raise.With<DelegateEventType>(arg1, arg2, ...);
```

I feel a little dirty introducing this singleton as a "wormhole" that connect the event-raising rule and the `Raise<T>` and `DelegateRaiser` classes, but could find no other way to access the arguments for the events.

An alternative to putting the instance in the class would've been to expose it from `Raise`, but that doesn't make me feel much better.