2.x: RxJavaPlugin.get/setXXX generics?

For unit tests I frequently bump into the restrictiveness of 

```java
RxJavaPlugins.setErrorHandler(Consumer<Throwable> handler);
```

I would like the signature to be 

```java
RxJavaPlugins.setErrorHandler(Consumer<? super Throwable> handler);
```

There are many more methods in `RxJavaPlugins` that could support lower and upper bounded wildcards. Can I make these changes?
