Another groupingReduce overload

[Michael Nascimento]

Hi guys,

Guava's uniqueIndex methods are pervasive in the code base I am using
to evaluate lambda:

http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/collect/Maps.html#uniqueIndex(java.lang.Iterable,
com.google.common.base.Function)

A groupingReduce overload like this would be very handy:

    public static <T, K> Collector<T, Map<K,T>>
groupingReduce(Function<? super T, ? extends K> classifier) {
        return groupingReduce(classifier, HashMap::new,
Functions.identity(), throwingMerger());
    }

Is it possible to have it? Please? :-)

Regards,
Michael