RAA - inverthash

Ruby's built-in Hash.invert function is BROKEN!

For a correctly implemented Hash.invert, you would expect:

     h.invert.invert == h 

to be true.. 

But what about:

    h = {"eins"=>1, "uno"=>1, "one"=>1, "two"=>2}

    h.invert
    => {1=>"one", 2=>"two"}

    h.invert.invert
    => {"two"=>2, "one"=>1}

THAT's BROKEN!


what we would expect is this:

    h.invert
    => {1=>["one", "eins", "uno"], 2=>"two"}
    h.invert.invert
    => {"uno"=>1, "two"=>2, "eins"=>1, "one"=>1}
    h.invert.invert == h
    => true

and that's what this implementation does for you..