Construct BrokenInputStream, BrokenReader, BrokenOutputStream, and BrokenWriter with RuntimeExceptions

I find BrokenReader very helpful  in tests of Reader exception handling, but at present, it can only be configured to throw IOException.  In some cases, I also want to test the handling of runtime exceptions, usually to test that they're propagated rather than caught.  To do this, I end up implementing a subclass of Reader.

It would be great if BrokenReader, and its close relatives BrokenInputStream, BrokenWriter, and BrokenOutputStream, could be configured to throw RuntimeExceptions in addition to IOExceptions.

I'll submit a PR for your consideration shortly.