[ELPA] New package: slime-volleyball

[Thomas Fitzsimmons]

Hi,

I'd like to include slime-volleyball in GNU ELPA, and move its
development to elpa.git, from:

   https://github.com/fitzsim/slime-volleyball

I have a local branch where I've replayed the history of that repository
into packages/slime-volleyball on the elpa.git master branch.

I've received a few small patches to the code; they're all fewer than 15
lines, so I think it's fine in terms of copyright assignment.

Thanks,
Thomas