Faster HashMap implementation

[Ismael Juma]

Hi Doug,

In a previous message you said:

"There are a few remaining things to consider
before taking this too seriously as a replacement.
I'll be out for 10 days starting tomorrow so probably
won't get a chance to do so soon."

I now understand the secret behind your productivity levels... somehow 10 days
for you is the same as 2 days for the rest of us. :)

More seriously, it would be great to have a HashMap that takes less memory and
performs as well or better so I am following this with interest. If things work
out, I'd be interested in borrowing the ideas for Scala's mutable HashMap (an
additional thing to take into account there is the ongoing specialization work).

Best,
Ismael