[Nimble] Add 'receiveNotification' matcher

I think the name of this matcher is backwards: it should be `post`, i.e.:

```swift
expect{
    NSNotificationCenter.defaultCenter().postNotificationName(UIApplicationDidBecomeActiveNotification, object: nil)
    return nil
}.will.post(UIApplicationDidBecomeActiveNotification)
```

Also, the matcher should support additional parameters:

```swift
expect{ /* ... */ }.will.post(UIApplicationDidBecomeActiveNotification)
expect{ /* ... */ }.will.post(UIApplicationDidBecomeActiveNotification, object: application)
expect{ /* ... */ }.will.post(UIApplicationDidBecomeActiveNotification, object: application, userInfo: ["token": "8675309"])
```

When `object` and `userInfo` are specified, it should only match if the notification is send from the correct object with the correct userInfo.